NRLF 


THE 


PHYSIOLOGY    OF    MM; 


DESIGNED   TO   REPRESENT 


THE    EXISTING    STATE    OF    PHYSIOLOGICAL 
SCIENCE, 


AS   APPLIED 


TO  THE  FUNCTIONS  OF  THE  HUMAN  BODY. 


BY 

AUSTIN   FLINT,    JR.,    I.D., 

PROFESSOR  OP   PHYSIOLOGY  AND  MICROSCOPY  IX  THE  BELLEVUE  HOSPITAL  MEDICAL  COLLEGE, 

NEW  YORK,   AND  IN  THE  LONG  ISLAND   COLLEGE  HOSPITAL  J  FELLOW  OF  THE  NEW 

YORK  ACADEMY  OF  MEDICINE,  MICROSCOPIST  TO  BELLEVUE   HOSPITAL. 


INTRODUCTION;     THE      BLOOD;      CIRCULATION; 
RESPIRATION". 


NEW  YORK: 
D.     APPLETON     AND     COMPANY, 

90,    92   &   94  GRAND    STREET. 
1870. 


PO  .^  0 


• 


ENTERED,  according  to  Act  of  Congress,  in  the  year  1865,  by 

D.  APPLETON  &  CO., 

In  the  Clerk's  Office  of  the  District  Court  of  the  United  States  for  the  Southern  District 

Fork. 


/. 


TO 

CHARLES   ROBIN, 

THE  FIKST  PROFE8SOB  OF  HISTOLOGY  IN  THE  FACULTY  OF  MEDICINE  OF  PABIS, 

AS  A  TOKEN   OF  APPEECIATION   OF  THE 
NUMEEOUS   OEIGINAL  EESEAEOHES  AND  DISCOVEEIES, 

PAETIOULAELY  IN 

HISTOLOGY   AND   PHYSIOLOGICAL   CHEMISTEY, 

BTZ   "WHICH  HE  HAS   CONTEIBTJTED   SO  LAEGELY  TO  BEING  THE  SCIENCE   OP 
PHYSIOLOGY   TO   ITS   PEESENT   CONDITION, 

AND  IN 

GEATEFUL  EEMEMBEANOE   OF  MANY   ACTS   OF   FEIENDSHIP, 
THIS   WOEK  IS   INSCEIBED   BY 

THE  AUTHOR. 


P  E  E  F  A  O  E. 


IN  entering  upon  the  labor  incident  to  the  preparation 
of  a  work  purporting  to  treat  comprehensively  of  the  physi- 
ology of  man,  the  author  appreciated  the  magnitude  of  the 
undertaking ;  and  the  special  study  which  it  necessarily  de- 
manded has  not  diminished  that  diffidence  with  which  a 
student  of  any  of  the  natural  sciences  puts  forward  a  book 
which  he  hopes  may  add  somewhat  to  existing  knowledge, 
or  fairly  represent  what  is  known  in  any  particular  depart- 
ment. In  assuming  so  grave  a  responsibility,  the  author 
should  be  actuated  by  a  sense  of  peculiar  fitness  for  his  task, 
as  well  as  a  conviction  that  literature  demands  such  a  work 
as  he  proposes  to  write.  Without  assuming  these  good  and 
sufficient  reasons,  the  author  of  the  present  volume  pleads  an 
earnest  desire  to  advance  the  science  of  physiology  and  facili- 
tate its  study ;  and  he  indulges  the  hope  that  he  may  be  in- 
strumental in  making  the  student  and  practitioner  of  medi- 
cine better  acquainted  with  what  must  be  conceded  to  be  the 
basis  of  true  pathology,  and  interest,  to  some  extent,  the  gen- 
eral reader  in  the  all-important  subject  of  human  physiology. 

The  plan  of  the  present  work  involves  a  consideration  of 


PEEFACE. 


pure  hum  an  physiology,  and  will  embrace  physiological 
chemistry  and  the  anatomy  of  the  tissues  and  organs  of  the 
body,  only  so  far  as  necessary  for  the  elucidation  of  the  func- 
tions of  the  organism.  Though,  undoubtedly,  the  chemistry 
and  general  anatomy  of  the  tissues  and  organs  strictly  belong 
to  physiology,  they  present  many  points  which  have  no  bear- 
ing, that  we  are  as  yet  able  to  comprehend,  upon  the  func- 
tions. In  the  present  condition  of  the  science,  a  considera- 
tion of  these  would  only  encumber  and  obscure  the  history 
of  the  physiological  processes.  While  it  is  undoubtedly  true 
that  every  advance  in  physiological  chemistry  or  histology 
will  have  its  bearing,  sooner  or  later,  upon  physiology,  it  is 
evident  that  discoveries  in  these  departments  must  be  multi- 
plied and  coordinated  before  their  relations  to  the  functions 
can  be  fully  appreciated.  Until  then  they  are  specially  inter- 
esting only  in  a  chemical  and  anatomical  point  of  view.  In 
the  same  way  every  discovery  in  physiology,  no  matter  how 
unimportant  it  may  at  first  appear  in  a  practical  point  of 
view,  will  eventually  have  its  bearing  upon  practical  medi- 
cine, surgery,  or  obstetrics ;  yet  it  will  not  find  its  way  into 
works  on  those  subjects  until  its  relations  become  apparent. 

As  an  introduction  to  the  study  of  physiology  proper,  a 
certain  amount  of  knowledge  of  physiological  chemistry  is 
indispensable.  It  is  in  this  direction  that  we  are  to  look  for 
advances  which  will  enable  us  to  comprehend  the  processes 
of  nutrition,  the  end  and  object  of  all  the  vegetative  functions 
of  the  body.  The  introduction,  then,  is  devoted  to  physiolog- 
ical chemistry.  No  attempt  has  been  made  to  treat  of  this 
subject  exhaustively,  or  to  include  a  consideration  of  all  the 
proximate  principles  which  have  been  isolated  and  studied. 
As  the  general  properties  and  relations  of  the  different  classes 


PREFACE.  7 

of  proximate  principles  are  by  far  the  most  important  to  us  as 
physiologists,  these  have  been  specially  dwelt  upon,  and 
their  relations  to  nutrition  followed  out  as  completely  as 
possible,  with  our  present  knowledge.  A  consideration  of 
the  excrementitious  proximate  principles,  being  connected 
exclusively  with  excretion,  has  been  deferred,  to  be  taken  up 
in  connection  with  that  function. 

In  treating  of  physiology  proper,  it  has  been  the  design 
of  the  author  to  present  what  is  actually  known  regarding 
the  functions  of  the  body ;  and  in  order  to  facilitate^  their 
study,  he  has  generally  commenced  the  consideration  of  in- 
dividual functions  with  a  sketch  of  the  physiological  anat- 
omy of  the  parts.  This  is  the  natural  point  of  departure  in 
the  thorough  investigation  of  any  special  function. 

The  science  of  physiology  dates  from  the  earliest  periods 
in  the  history  of  medicine;  and  certain  important  physio- 
logical facts  were  demonstrated  experimentally  hundreds  of 
years  ago.  "While  the  author  has  regarded  purely  historical 
considerations,  and  discussions  of  mere  theoretical  questions, 
as  unprofitable,  he  has  attempted  to  give  due  credit  to  those 
who,  by  their  experiments  and  observations,  have  contributed 
to  bring  the  science  to  its  present  condition.  With  this  view, 
he  has  procured  and  consulted,  as  far  as  possible,  accounts  of 
original  investigations ;  but  from  the  poverty  in  physiologi- 
cal works  of  the  public  libraries  to  which  he  has  had  access, 
it  has  been  necessary  to  depend  to  a  certain  extent  on  the 
exhaustive  treatises  on  physiology  published  in  other  coun 
tries.  Though,  undoubtedly,  he  has  been  unable  in  all  in- 
stances to  give  due  credit  to  every  observer,  this  has  been 
attempted  as  far  as  possible. 

It  is  an  undoubted  fact   that  nearly  all  the  important 


8  PREFACE. 

developments  in  physiology  have  been  the  result  of  experi 
ments  upon  living  animals,  by  vivisections  or  otherwise,  or 
accurate  experimental  observations  upon  the  human  subject. 
The  great  extension  of  this  method  of  study  is  the  cause  of 
the  rapid  advances  the  science  is  making  at  the  present  day. 
For  some  years  the  author  has  f>een  in  the  habit  of  employ- 
ing vivisections  in  public  teaching,  and  in  this  way  has  fre- 
quently verified  the  observations  of  the  earlier  as  well  as  the 
more  modern  physiologists.  A  frequent  repetition  of  experi- 
ments has  often  enabled  him  to  reconcile  the  discordant  results 
of  the  observations  of  others ;  and  following  out  new  questions 
which  have  presented  themselves  in  the  constant  observa- 
tion of  the  living  organs,  he  has  advanced  some  original 
views  regarding  certain  of  the  functions.  A  new  method  is 
likewise  presented  for  the  analysis  of  the  blood  with  reference 
to  its  organic  constituents. 

The  plan  of  publication  of  the  present  work  is  one  which 
is  novel  in  this  country,  but  which  has  been  adopted  abroad, 
particularly  in  France,  in  almost  all  elaborate  treatises  on  phys- 
iology. It  is  to  be  issued  in  separate  parts,  each,  however, 
forming  a  distinct  treatise  devoted  to  natural  subdivisions  of 
the  subject.  The  volume  now  issued  embraces  an  Introduc- 
tion, the  Blood,  Circulation,  and  Respiration.  The  remain- 
ing volumes,  three  in  number,  will  be  issued  yearly  until  the 
work  is  finished,  and  will  likewise  be  severally  complete  in 
themselves.  Simple  and  well-known  anatomical  and  physi- 
ological points  have  not  been  illustrated  by  engravings, 
which  have  only  been  introduced  where  they  seemed  neces- 
sary to  elucidate  the  text. 

NEW  YORK,  October,  1865. 


CONTENTS. 


INTRODUCTION. 

General  considerations — Vital  properties  of  organized  structures — Proximate 
principles — Inorganic  principles — Organic  non-nitrogenized  principles — Or- 
ganic nitrogenized  principles, Page  13 

CHAPTER  I. 

THE   BLOOD. 

General  considerations — Transfusion — Quantity — Physical  characters — Opacity — 
Temperature — Specific  gravity — Color — Anatomical  elements  of  the  blood — 
Eed  corpuscles — Chemical  characters  of  red  corpuscles — Development  of  red 
corpuscles — Formation  of  red  corpuscles — Leucocytes,  or  white  corpuscles — 
Development  of  leucocytes, ,  .  95 

CHAPTER  II. 

COMPOSITION   OP   THE   BLOOD. 

General  considerations — Methods  of  quantitative  analysis— Fibrin — Corpuscles — 
Albumen — Inorganic  constituents — Sugar — Fatty  emulsion — Coloring  matter 
of  the  serum — Urea  and  the  urates — Cholesterine — Creatine — Creatinine,  127 

CHAPTER  III. 

COAGULATION  OP  THE  BLOOD. 

General  considerations — Characters  of  the  clot— Characters  of  the  serum — Coagu- 
lating principle  in  the  blood — Circumstances  which  modify  coagulation — Co- 
agulation of  the  blood  hi  the  organism— Spontaneous  arrest  of  hemorrhage — 
Cause  of  coagulation  of  the  blood — Summary  of  the  properties  and  functions 
of  the  blood, .142 


10  CONTENTS. 

CHAPTER  IY. 

CIRCULATION   OF   THE   BLOOD. 

Discovery  of  the  circulation — Physiological  anatomy  of  the  heart — Valves  of  the 
heart — Movements  of  the  heart — Impulse  of  the  heart — Succession  of  move- 
ments of  the  heart — Force  of  the  heart — Action  of  the  valves — Sounds  of  the 
heart— Cause  of  the  sounds  of  the  heartj  ....  Page  170 

CHAPTER  V. 

FREQUENCY  OF  THE  HEAET's  ACTION. 

Frequency  of  the  heart's  action — Influence  of  age — Influence  of  digestion — Influ- 
ence of  posture  and  muscular  exertion — Influence  of  exercise — Influence  of 
temperature — Influence  of  respiration  on  the  action  of  the  heart — Cause  of 
the  rhythmical  contractions  of  the  heart — Influence  of  the  nervous  system  on 
the  heart — Division  of  the  pneumogastrics — Galvanization  of  the  pneumogas- 
trics — Causes  of  the  arrest  of  action  of  the  heart — Blows  upon  the  epigas- 
trium,    .  .211 

CHAPTER  VI. 

CIRCULATION   OF   THE  BLOOD   IN   THE   ARTERIES. 

Physiological  anatomy  of  the  arteries — Course  of  blood  in  the  arteries — Elasticity 
of  the  arteries — Contractility  of  the  arteries — Locomotion  of  the  arteries  and 
production  of  the  pulse — Form  of  the  pulse — Sphygmograph — Pressure  of 
blood  in  the  arteries — Hemodynamometer — Cardiometer — Differential  cardio- 
meter — Pressure  in  different  parts  of  the  arterial  system — Influence  of  respi 
ration  on  the  arterial  pressure— Effects  of  hemorrhage — Rapidity  of  the -cur- 
rent of  blood  in  the  arteries — Instruments  for  measuring  the  rapidity  of  the 
arterial  circulation — Variations  in  rapidity  with  the  action  of  the  heart — Ra- 
pidity hi  different  parts  of  the  arterial  system — Arterial  murmurs,  .  .  240 

CHAPTER  VII. 

CIRCULATION   OF   THE   BLOOD   IN  THE   CAPILLARIES. 

Distinction  between  capillaries  and  the  smallest  arteries  and  veins — Physiological 
anatomy  of  the  capillaries — Peculiarities  of  distribution — Capacity  of  the 
capillary  system — Course  of  blood  in  the  capillaries — Phenomena  of  the 
capillary  circulation — Rapidity  of  the  capillary  circulation — Relations'  of  the 
capillary  circulation  to  respiration — Causes  of  the  capillary  circulation — In- 
fluence of  temperature  on  the  capillary  circulation — Influence  of  direct  irrita- 
tion on  the  capillary  circulation,  .  .  .  .  .  .  .  278 


CONTENTS.  11 

CHAPTEE  VIII. 

CIRCULATION  OP  THE  BLOOD  IN  THE  VEINS. 

Physiological  anatomy  of  the  veins — Strength  of  the  coats  of  the  veins — Valves 
of  the  veins — Course  of  the  blood  in  the  veins — Pressure  of  blood  in  the 
veins — Rapidity  of  the  venous  circulation — Causes  of  the  venous  circulation — 
Influence  of  muscular  contraction — Air  in  the  veins — Function  of  the  valves — 
Yenous  anastomoses — Conditions  which  impede  the  venous  circulation — Re- 
gurgitant  venous  pulse, Page  301 

CHAPTER  IX. 

PECULIARITIES  OF   THE  CIRCULATION  IN   DIFFERENT  PARTS   OF   THE  SYSTEM. 

Circulation  in  the  cranial  cavity — Circulation  hi  erectile  tissues — Derivative  circu- 
lation— Pulmonary  circulation — General  rapidity  of  the  circulation — Time  re- 
quired for  the  passage  through  the  heart  of  all  the  blood  in  the  organism — 
Relations  of  the  general  rapidity  of  the  circulation  to  the  frequency  of  the 
heart's  action — Phenomena  hi  the  circulatory  system  after  death,  .  .  332 

CHAPTER  X. 

RESPIRATION. 

General  considerations — Physiological  anatomy  of  the  respiratory  organs — Respi- 
ratory movements  of  the  larynx — Epiglottis — Trachea  and  bronchial  tubes — 
Parenchyma  of  the  lungs — Carbonaceous  matter  in  the  lungs — Movements  of 
respiration — Inspiration — Muscles  of  inspiration — Action  of  the  diaphragm — 
Action  of  the  scaleni— Intercostal  muscles — Levatores  costarum — Auxiliary 
muscles  of  inspiration, 353 

CHAPTER  XI. 

MOVEMENTS   OF   EXPIRATION. 

Influence  of  the  elasticity  of  the  pulmonary  structure  and  walls  of  the  chest — 
Muscles  of  expiration — Internal  intercostals — Infra-costales — Triangularis  ster- 
ni — Action  of  the  abdominal  muscles  in  expiration — Types  of  respiration — 
Abdominal  type — Inferior  costal  type — Superior  costal  type — Frequency  of  the 
respiratory  movements — Relations  of  inspiration  and  expiration  to  each  other — 
The  respiratory  sounds — Coughing — Sneezing — Sighing — Yawning — Laugh- 
ing— Sobbing — Hiccough — Capacity  of  the  lungs  and  the  quantity  of  air 
changed  in  the  respiratory  acts — Residual  air — Reserve  air — Tidal,  or  breathing 
air — Complemental  air — Extreme  breathing  capacity — Relations  in  volume  of 
the  expired  to  the  inspired  air — Diffusion  of  air  in  the  lungs,  .  .  .  382 


12  CONTENTS. 

CHAPTER  XII. 

CHANGES   WHICH   THE  AIE   UNDERGOES   IN   RESPIRATION. 

General  considerations — Discovery  of  carbonic  acid — Discovery  of  oxygen — Com- 
position of  the  air — Consumption  of  oxygen — Influence  of  temperature — In- 
fluence of  sleep — Influence  of  an  increased  proportion  of  oxygen  in  the  atmos- 
phere— Temperature  of  the  expired  air— inhalation  of  carbonic  acid — Influence 
of  age — Influence  of  sex — Influence  of  digestion — Influence  of  diet — Influence 
of  sleep — Influence  of  muscular  activity — Influence  of  moisture  and  tem- 
perature— Influence  of  seasons — Relations  between  the  quantity  of  oxygen 
consumed  and  the  quantity  of  carbonic  acid  exhaled — Exhalation  of  watery 
vapor — Exhalation  of  ammonia — Exhalation  of  organic  matter — Exhalation 
of  nitrogen, Page  409 

CHAPTER  XIII. 

CHANGES    OF   THE   BLOOD   IN  RESPIRATION. 

Difference  in  color  between  arterial  and  venous  blood — Comparison  of  the  gases 
in  venous  and  arterial  blood — Observations  of  Magnus — Analysis  of  the  blood 
for  gases — Relative  quantities  of  oxygen  and  carbonic  acid  in  venous  and  ar- 
terial blood — Nitrogen  of  the  blood — Condition  of  the  gases  in  the  blood — 
Mechanism  of  the  interchange  of  gases  between  the  blood  and  the  air  in 
the  lungs — General  differences  in  the  composition  of  arterial  and  venous 
blood, 452 

CHAPTER  XIV. 

RELATIONS   OP  RESPIRATION  TO  NUTRITION,  ETC. 

Views  of  physiologists  anterior  to  the  time  of  Lavoisier — Relations  of  the  con- 
sumption of  oxygen  to  nutrition — Relations  of  the  exhalation  of  carbonic  acid 
to  nutrition — Essential  processes  of  respiration— The  respiratory  sense,  or 
want  on  the  part  of  the  system  which  induces  the  respiratory  movements — 
Location  of  the  respiratory  sense  in  the  general  system — Sense  of  suffocation 
— Respiratory  efforts  before  birth — Cutaneous  respiration — Asphyxia,  .  472 


PHYSIOLOGY    OF   MAN. 


INTRODUCTION. 

General  considerations — Vital  properties  of  organized  structures — Proximate  prin- 
ciples— Inorganic  principles — Organic  non-nitrogenized  principles — Organic 
nitrogenized  principles. 

THE  epoch  of  purely  speculative  reasoning,  without  the 
basis  of  established  facts  sufficient  to  justify  any  connected 
theories,  belongs  to  the  remote  history  of  Natural  Science. 
The  ideas  of  the  great  philosophers  of  ancient  times,  who 
studied  Nature  by  what  may  be  called  the  intuitive  method, 
have  been  gradually  giving  place  to  doctrines  based  on  the 
observation  and  investigation  of  phenomena.  Ages  of  obser- 
vation and  generalization  of  facts  by  the  greatest  intellects 
have  put  us  but  little  beyond  the  threshold  of  the  great 
domain  of  Science.  But  we  have  learned  enough  to  know 
that  all  Nature  is  regulated  by  immutable  laws.  Students 
of  her  divine  mysteries  should  be  more  than  content  if  per- 
mitted to  discover  some  of  the  truths,  the  development  of 
which  marks  the  scientific  advancement  of  each  succeeding 
age,  though  they  may  seem  an  insignificant  portion  of  what 
is  to  be  learned.  It  is  only  by  accurate  observation  and 
generalization  of  a  sufficient  number  of  phenomena,  that  the 
laws  of  Nature  are  to  be  discovered.  They  are  the  creation 


14  INTRODUCTION. 

of  an  infinite  wisdom  which  never  errs.  We  cannot  hope  to 
arrive  at  a  knowledge  of  them  by  pure  reasoning;  or  by 
assuming  that  they  are  in  accordance  with  definite  principles, 
too  often  the  offspring  of  our  own  limited  intellects.  Never- 
theless, it  is  a  physiological  attribute  of  the  human  mind  to 
desire  to  press  on  in  advance  of  observation,  and  to  form 
theories,  which  may  or  may  not  be  carried  out  by  the  suc- 
ceeding development  of  actual  knowledge.  Theories  which 
are  not  built  upon  false  or  imperfectly  observed  phenomena, 
are  the  pioneers  of  actual  discovery.  When  theoretical  pre- 
conceptions are  justified  and  corrected  by  original  observa- 
tions and  experiments,  with  the  brain  to  conceive  and  the 
will  to  execute,  man,  in  thus  working  out  the  great  problems 
of  Nature,  is  fulfilling  one  of  the  highest  purposes  of  his 
existence. 

With  the  few  facts  which  were  at  first  known,  the 
ancient  speculative  philosophy  professed  to  embrace  the 
whole  of  natural  science ;  but  as  discoveries  were  made  in 
different  departments,  a  division  of  labor  became  necessary. 
We  now  find  different  classes  of  scientific  men,  each  working 
in  a  particular  sphere ;  as  in  the  lower  zoological  divisions, 
a  single  organ  performs  all  the  varied  functions  of  nutrition, 
while  in  the  higher  orders,  when  the  processes  of  life  are 
more  intricate  and  complicated,  the  system  is  divided  up 
into  elaborately-organized  parts,  each  of  which  has  an  allotted 
office. 

From  the  time  of  Galen  may  be  said  to  date,  as  distinct 
from  astronomy,  chemistry  (or  rather  alchemy),  physics,  &c., 
the  science  which  is  now  called  PHYSIOLOGY. 

Physiology,  from  its  etymology,  signifies  the  science  of 
Nature ;  but  in  the  sense  in  which  the  term  is  now  used,  it 
may  be  defined  to  be  the  science  of  life.  More  elaborate  defi- 
nitions have  been  given,  but  they  only  qualify  and  explain  the 
meaning  of  what  we  know  as  life. 

A  natural  division  of  physiology  is  into  animal  and 
vegetable;  and  again,  into  the  physiology  of  the  inferior 


GENERAL   CONSIDERATIONS.  15 

animals  as  compared  with  man,  or  comparative  physiology, 
and  the  PHYSIOLOGY  OF  MAN.  The  latter,  which  is  the  sub- 
ject of  the  present  work,  is  peculiarly  interesting  to  the 
physician,  as  the  basis  of  all  accurate  knowledge  of  the 
science  of  medicine. 

In  the  early  history  of  physiological  science,  the  develop- 
ment of  anatomy  necessarily  gave  us  much  information  con- 
cerning the  functions  of  the  body ;  and  we  now  have  to 
acknowledge  our  continual  indebtedness  to  anatomical  inves- 
tigations, particularly  those  made  with  the  aid  of  the  micro- 
scope, for  important  advancements  in  physiology.  In  treating 
of  the  subject,  it  is  impossible  to  neglect  what  is  most  appro- 
priately called  the  physiological  anatomy  of  parts,  a  knowl- 
edge of  which  alone  enables  us,  oftentimes,  to  comprehend 
their  functions.  For  example,  we  can  scarcely  conceive  how 
the  anatomy  of  the  circulatory  system  could  be  clearly  under- 
stood without  giving  us  a  knowledge  of  its  physiology. 

Chemistry,  also,  when  the  components  of  the  body  are 
studied  in  such  a  way  as  not  to  destroy  their  properties  as 
organic  compounds,  has  a  most  important  bearing  on  the 
advancement  of  physiology.  As  a  striking  example  of  this, 
we  may  take  the  discovery  of  the  properties  of  the  gases  of 
the  air  and  their  relations  to  the  blood  by  Lavoisier,  which 
gave  us  the  first  definite  ideas  regarding  the  essential  phe- 
nomena of  respiration.  We  are  now  largely  indebted  to 
modern  physiological  chemistry  for  a  knowledge  of  many  of 
the  essential  phenomena  of  life,  and  look  to  a  further  develop- 
ment of  this*  science  for  an  elucidation  of  many  important, 
but  still  obscure,  questions  connected  with  nutrition. 

Certain  physiological  functions  are  in  exact  accordance 
with  established  physical  laws ;  which  are  competent,  for 
example,  to  explain  the  refraction  in  the  structures  of  the 
eye,  or  the  conduction  of  vibrations  in  the  ear.  Physical 
laws  are  involved  in  most  of  the  phenomena  of  life,  but  are 
generally  more  or  less  modified  by  the  peculiar  properties  of 
organized  bodies. 


16  INTRODUCTION. 

Many  of  the  phenomena  of  life  are  made  clear  by  a 
comparison  of  the  physiology  of  man  with  that  of  the  infe- 
rior animals,  which  is  often  simpler  and  more  easily  investi- 
gated. 

As  physiology  is  the  natural  and  only  correct  basis  of 
pathology,  we  frequently  derive  important  information  as 
to  the  functions  of  parts  by  studying  the  effects  of  disease, 
by  which  their  functions  are  modified  or  abolished.  The 
experiments  thus  performed  by  Nature  on  the  human  system 
are  frequently  more  instructive  than  those  which  we  make 
on  the  inferior  animals. 

As  the  complement  to  anatomy,  human  and  comparative, 
organic  chemistry,  and  pathology,  we  have  as  the  most  pre- 
cious and  fruitful  means  of  physiological  investigation,  direct 
observation  of  the  phenomena  of  life  in  man  and  the  inferior 
animals,  and  experiments  on  animals  by  vivisections.  The 
present  condition  of  physiology  is  a  testimony  of  the  incal- 
culable value  of  this  method  of  study.  "Were  it  consistent 
with  our  plan  to  follow  out  the  general  development  of  the 
science  from  an  historical  point  of  view,  we  should  find  the 
names  of  Harvey,  Aselli,  Haller,  Hales,  Spallanzani,  Ed- 
wards, Bichat,  Bell,  Majendie,  and  a  host  of  others,  bearing 
witness  by  their  works  to  the  value  of  vivisections  in  physio- 
logical investigations ;  to  say  nothing  of  the  great  observers 
of  the  present  day,  who  are  constantly  adding  to  our  knowl- 
edge. The  field  would  be  sterile  indeed  were  it  not  for 
experiments  on  living  animals ;  and  the  loss  to  the  science 
which  has  for  its  object  the  alleviation  of  the  sufferings  of 
mankind,  would  have  been  incalculable,  had  physiologists 
been  unwilling,  from  false  motives  of  humanity,  to  inflict 
pain  upon  the  lower  animals,  which  is  to  a  certain  extent 
unavoidable  in  experimentation. 

Physiological  literature,  in  the  great  Elementa  Physiolo- 
gioB  of  Haller,  which  belonged  to  a  past  generation,  and 
the  elaborate  systematic  works  of  Berard,1  Longet,  Miiller, 

1  Berard  did  not  live  to  complete  his  great  work  on  physiology.     He  died 


GENERAL   CONSIDERATIONS.  IT 

and  other  experimentalists  of  the  present  generation,  fur- 
nishes abundant  proof  that  the  faculty  of  observation  and  the 
power  of  generalization  are  not  necessarily  inconsistent  with 
each  other. 

It  would  be  futile  to  attempt  to  point  out  all  the  difficul- 
ties and  sources  of  error  in  experimentation  on  living  animals. 
These  must  be  overcome  by  the  physiologist  after  he  has 
become  practically  acquainted  with  them.  It  must  be  borne 
in  mind,  however,  that  we  are  interrogating  Nature ;  and 
our  sole  aim  must  be  to  put  our  questions  intelligently  and 
interpret  the  answers  correctly.  She  does  not  unfold  her 
mysteries  to  the  careless  and  inconsiderate  observer.  An 
accident  may  lead  the  reflecting  student  to  frame  a  particular 
set  of  experiments,  for  the  explanation  of  an  unexpected 
phenomenon ;  but  we  should  go  to  work  with  an  idea  of  what 
we  wish  to  know,  always  ready  to  correct  or  abandon  our 
most  cherished  preconceived  notions  if  we  find  they  are  not 
in  accordance  with  facts.  Experiments  should  not  be  isolat- 
ed. A  golden  opportunity  is  thrown  away  if  we  stop  short 
of  the  end  in  a  legitimate  series  of  investigations ;  for  none 
are  better  fitted  to  go  through  the  later  steps  of  a  natural 
series  of  experiments  than  they  who  have  conceived  and 
executed  the  first. 

With  the  many  varying  conditions  of  the  system  which 
inevitably  occur  in  living  animals,  it  is  almost  unnecessary  to 
add  that  an  important  observation  should  be  repeatedly  con- 
firmed, and  the  answer  to  our  experimental  inquiries  obtained, 
if  possible,  in  different  ways.  It  must  be  remembered  that 
Nature  never  contradicts  herself,  and  has  no  exceptions. 
Her  laws  are  invariable ;  and  if  experiments  are  apparently 
contradictory,  we  must  look  for  differences  in  the  conditions 

shortly  after  he  had  commenced  the  publication  of  the  fourth  volume  in  1855.  The 
prolegomenes,  and  the  sections  on  digestion,  absorption,  the  blood,  respiration, 
and  circulation,  are  perhaps  the  most  candid,  exhaustive,  and  best  considered 
essays  on  these  subjects  in  any  language.  Science  suffered  a  great  loss  when 
the  author  was  thus  cut  off  in  the  midst  of  his  labors. 
2 


18  INTRODUCTION. 

under  which  the  observations  were  made.  It  would  be 
always  possible  to  reconcile  discordant  results  of  observations, 
were  we  able  to  entirely  appreciate  the  conditions  under 
which  they  were  made.  For  this  reason,  a  practical  physiolo- 
gist, if  entirely  unbiassed,  is  most  competent  to  judge  of,  and 
assimilate,  the  observations  of  others. 

Vital  Properties  of  Organized  Structures. — In  com- 
mencing the  study  of  physiology,  we  should  have  some  idea 
of  the  physiological  chemistry  of  the  body,  comprehending 
fully,  in  the  first  place,  what  is  meant  by  life,  or  the  vital 
properties  of  the  tissues. 

The  tissues  which  are  endowed  with  vitality  are  in  a 
state  of  continual  metamorphosis,  more  or  less  active  accord- 
ing to  their  degree  of  organization.  They  are  constantly 
undergoing  transformation  into  what  are  known  as  effete 
matters  and  have  the  property  of  appropriating,  in  the  great 
majority  of  instances  from  the  blood,  material  for  their  re- 
generation. In  other  words,  under  proper  conditions,  living 
tissues  have  the  property  of  self-regeneration.  This  constant 
waste,  or  physiological  disintegration,  is  known  under  the 
name  of  destructive  assimilation,  and  its  products  are  called 
excretions.  The  power  of  self-regeneration  is  called  nutrition. 

This  property  affects  all  the  constituents  of  the  body 
without  exception.  We  shall  see  that  physiological  chemis- 
try divides  the  constituents  of  the  organism  into  organic  and 
inorganic  principles ;  the  latter  being  identical  with  princi- 
ples found  in  the  inorganic  world.  Inorganic  principles,  in 
the  living  body,  are  always  in  union  with  organic  principles ; 
they  are  regularly  thrown  off  with  the  products  of  their  de- 
structive assimilation,  and  are  supplied  to  the  parts,  as  a 
necessity  of  nutrition.  They  never  exist  in  their  crystalline 
form,  in  which  they  so  commonly  occur  in  the  inorganic 
kingdom.1  Every  part  of  the  body  either  is,  or  has  been, 

*  There  is  a  single  exception  to  this  law  in  the  crystals  of  carbonate  of  lime 
which  are  found  in  the  internal  ear,  constituting  the  otoconies  or  otoliths. 


THE   PROPERTIES   OF   ORGANIZED   STRUCTURES.  19 

endowed  with  life.  Some  are  desquamated  and  reproduced, 
like  the  nails,  hair,  or  epidermis ;  some  are  worn  away  and 
not  reproduced,  like  the  enamel  of  the  teeth ;  but  they  are 
all  subject  to  vital  laws  in  their  formation,  and  the  exceptions 
to  the  law  that  each  tissue  has  the  property  of  self-regenera- 
tion are  very  few. 

The  power  of  self-regeneration  of  organized  tissues  does 
not  exist  indefinitely.  After  a  time  the  tissues  fail  to  appro- 
priate enough  organic  matter  to  entirely  supply  the  waste  ; 
they  gradually  degenerate,  and  finally  die,  as  a  necessary 
condition  of  their  existence.  The  activity  of  the  regenerat- 
ing powers  seems  to  depend  on  the  proportion  of  organic 
matter  which  the  tissues  contain.  In  childhood,  when,  as  a 
condition  of  growth,  the  nutrition  is  greater  than  the  waste, 
the  organic  matter  of  the  tissues  is  in  excess.  In  old  age 
calcareous  deposits  are  frequent,  and  the  inorganic  matter 
in  all  parts  is  in  excess,  until  finally  the  organs  become  inca- 
pable of  performing  their  functions. 

The  properties  above  mentioned  serve  to  distinguish 
organized  living  bodies  from  those  not  endowed  with  life. 
Man,  in  the  general  properties  of  his  tissues  and  organs, 
does  not  differ  from  the  higher  classes  of  the  inferior  animals, 
as  the  mammalia.  Their  tissues  are  as  highly  organized, 
and  the  various  functions  connected  with  nutrition,  such  as 
secretion,  digestion,  circulation,  respiration,  etc.,  are  essen- 
tially the  same.  In  some  instances,  as  in  the  digestive  func- 
tion of  some  of  the  herbivora,  the  process  is  even  more 
elaborate  than  in  the  human  subject.  For  this  reason, 
with  proper  precautions,  we  can  apply  without  hesitation 
most  experiments  on  the  mammalia  to  the  physiology  of 
man. 

To  the  development  of  the  great  centre  of  the  nervous 
system,  man  owes  his  preeminence  in  the  animal  scale.  In 
the  wTords  of  Longet:  "In  his  psychical  relations,  but  in 
these  only,  man  can  constitute  a  distinct  kingdom.  Physi- 
ology has  specially  in  view  the  acts  which  assimilate  man  to 


20  INTRODUCTION. 

animals  ;  it  belongs  to  psychology  to  study  and  make  known 
the  faculties  which  separate  him  from  them."  1 

Even  without  accidents,  physiological  death  is  a  necessity 
of  existence  ;  but  nature  has  provided,  as  one  of  the  most  im- 
portant attributes  of  organization,  a  means  by  which  organ- 
ized bodies  may  be  perpetuatedjhrough  all  ages.  In  the  fully- 
developed  organism  are  produced  two  kinds  of  organic  ele- 
ments, the  male  and  the  female.  These,  when  brought  in 
contact  with  each  other  under  proper  conditions,  are  capable 
of  being  developed  into  a  new  being,  similar  in  organization 
to,  and  designed  to  take  the  place  of^  the  one  which  is  to  pass 
away.  These  new  beings  are  generated  in  sufficient  number 
to  insure  the  perpetuation  of  the  species. 

The  excrementitious  products  of  the  body  during  life,  and 
the  body  itself  after  death,  changed  by  the  peculiar  process 
of  putrefaction,  are  returned  to  the  earth  and  to  the  air,  and 
contribute  to  the  nutrition  of  the  vegetable  kingdom.  The 
vegetables,  in  their  turn,  are  consumed  in  the  nutrition  of 
animals.  All  the  elements  necessary  to  nutrition,  except 
oxygen,  are  taken  into  the  alimentary  canal  as  food.  Our 
food  consists  either  of  vegetables,  or  the  flesh  of  animals  that 
are  nourished  by  vegetables. 


PROXIMATE   PRINCIPLES. 

From  the  preceding  general  remarks,  it  is  evident  that 
physiology,  to  be  systematically  and  properly  studied,  must 
be  connected  with  physiological  anatomy  and  chemistry. 
The  physiological  anatomy  of  special  organs  and  systems 
naturally  precedes  the  consideration  of  their  functions ;  and  in 
treating  of  the  functions  of  other  parts,  more  especially  the 
nutritive  and  excrementitious  fluids  and  the  secretions,  we 
are  unavoidably  led  to  consider  fully  their  chemical  constitu- 
tion. There  are,  however,  certain  constituents  of  the  body, 

1  LONGET,  TraitS  dc  Physiologic,  Paris,  1861,  tome  i.,  p.  xxviii. 


PROXIMATE  PRINCIPLES.  21 

a  full  consideration  of  which,  in  connection  with  special 
functions,  would  be  out  of  place,  as  well  as  many  points  in 
physiological  chemistry,  showing  the  relations  of  the  different 
elements  to  nutrition,  etc. ;  hence  is  desirable,  as  an  intro- 
duction to  physiology  proper,  a  brief  review  of  the  prox- 
imate principles  of  the  economy.  In  this  introduction  it  is 
not  proposed  to  treat  exhaustively  of  physiological  chemistry. 
Such  principles  as  will  demand,  from  their  connection  with 
special  functions,  extended  consideration  in  another  place, 
are  omitted  or  simply  alluded  to,  as  well  as  some  which  have 
a  very  unimportant  or  obscure  function. 

If  we  were  to  study  the  constitution  of  the  body  from  a 
purely  chemical  point  of  view,  it  would  be  divided  into 
elementary  substances,  or  those  which  are  absolutely  incapa- 
ble of  further  subdivision.  In  this  way  we  should  lose  all 
distinction  between  organic  matters  and  those  which  enter 
indifferently  into  the  composition  of  all  bodies  in  Nature, 
whether  inert  or  endowed  with  vital  properties.  After 
having  thus  ascertained  the  ultimate  constitution  of  the 
organism,  we  have  learned  all  that  is  possible  by  this  method ; 
for  we  are  already  familiar  with  the  properties  and  be- 
havior of  elementary  matter,  as  obtained  from  the  inorganic . 
kingdom. 

In  physiological  chemistry  this  method  is  inadmissible. 
The  substances  which  are  presented  for  our  study  in  the 
living  organism  are  endowed  with  vital  properties.  Their 
ultimate  composition  is  of  little  consequence  compared  with 
a  knowledge  of  the  laws  which  regulate  their  behavior,  not 
as  elements,  but  as  constituents  of  an  elaborate  vital  organi- 

'  O 

zation. 

We  can  separate  from  the  organism  of  animals  substances 
of  a  peculiar  nature  which  are  never  found  in  the  inorganic 
world.  These  demand  our  special  consideration.  If  we 
attempt  to  study  them  by  the  ordinary  chemical  processes  of 
analysis,  they  are  destroyed  and  lose  their  properties  as 
organic  principles. 


22  INTEODTJCTION. 

Combined  with  these  organic  principles  we  always  have 
a  certain  proportion  of  inorganic  matters  which  may,  it  is 
true,  be  separated  from  them  easily,  and  apparently  without 
decomposition,  but  which  are,  notwithstanding,  necessary  to 
the  peculiar  properties  by  which  we  recognize  organic  sub- 
stances. Their  physiological  union  is  so  intimate  that  they 
may  justly  be  considered  as  organic,  though  originating  in 
the  inorganic  kingdom. 

Chemistry  recognizes  fifty-nine  elementary  substances,  of 
which  some  fifteen  or  eighteen  enter  into  the  constitution  of 
the  human  body ;  but  as  physiologists,  we  must  make  a 
division  of  the  body  into  component  principles,  without 
reference  to  the  elementary  substances  themselves,  but  with 
a  view  to  the  form  and  condition  of  their  existence  in  the 
organism.  As  we  have  seen  that  the  distinguishing  properties 
of  organic  principles  are  destroyed  when  they  are  reduced  to 
their  ultimate  elements,  it  is  evident  that  many  or  most  of 
the  principles  into  which  the  body  is  divided  physiologically 
are  compound  substances. 

From  this  point  of  view,  the  organism  may  be  said  to  be 
composed  of  Immediate  or  Proximate  Principles. 

A  Proximate  Principle  may  be  defined  to  be  a  substance 
extracted  from  the  l>ody,  which  cannot  be  further  subdivided 
without  chemical  decomposition  and  loss  of  its  characteristic 
properties. 

According  to  Robin  and  Yerdeil,  there  exist  from  eighty- 
five  to  ninety  distinct  proximate  principles  in  the  human 
body.1 

The  distinction  between  proximate  principles  and  chem- 
ical elements  is  apparent  from  the  definition  above  given. 
To  illustrate  this  difference,  however,  we  may  take  the  fol- 
lowing example.  Chloride  of  sodium  is  an  important  proxi- 
mate principle,  and  is  composed  of  the  chemical  elements 
chlorine  and  sodium.  As  chloride  of  sodium,  it  has  certain 

1  ROBIN  and  VERDEIL,  Chimie  Anatomique  et  Physiologique,  Paris,  1853, 
tome  L,  p.  128. 


PKOXIMATE   PKINCIPLES. 

properties,  and  is  endowed  with  certain  functions  in  the  econ- 
omy, which  are,  of  course,  entirely  different  from  the  proper- 
ties of  chlorine  or  sodium ;  the  latter  especially  being  only 
obtained  in  a  state  of  chemical  purity  by  a  difficult  and  elab- 
orate process  of  manipulation.  As  physiologists  we  have 
nothing  to  do  with  the  properties  of  chlorine,  or  the  rare 
metal  sodium  ;  we  only  wish  to  know  as  much  as  possible 
about  the  functions  of  these  two  bodies  united  to  form  com- 
mon salt.  Again,  fibrin,  a  proximate  principle  found  in  the 
blood,  may  be  reduced  by  chemical  manipulations  to  a  cer- 
tain number  of  atoms  of  carbon,  hydrogen,  oxygen,  nitrogen, 
and  sulphur.  But  a  knowledge  of  even  the  exact  proportions 
of  these  ingredients  would  be  of  no  practical  benefit,  if  we 
were  unacquainted  with  the  general  properties  of  fibrin  and 
its  uses  in  the  economy.  Salt  cannot  be  subdivided  into 
chlorine  and  sodium,  nor  fibrin  into  its  elements,  without. 
chemical  decomposition  and  loss  of  characteristic  proper- 
ties /  but  both  of  these  substances  can  be  extracted  from  the 
body  in  the  condition  in  which  they  exist  in  the  organism, 
and  are  therefore  proximate  principles. 

A  constituent  of  the  body  may  be  at  the  same  time  a 
chemical  element  and  a  proximate  principle.  An  example 
of  this  is  the  free  oxygen  in  solution  in  the  blood.  This 
enjoys,  in  the  body,  the  properties  of  free  oxygen,  and  may 
be  extracted  from  the  blood  by  mere  displacement  with  an- 
other gas,  or  by  the  air-pump ;  a  process  quite  different  from 
the  elaborate  chemical  manipulation  which  would  be  neces- 
sary to  obtain  oxygen  by  decomp'osition  of  fibrin,  albumen, 
or  any  compound  principle. 

The  principles  which  compose  the  body,  with  the  excep- 
tion of  excrementitious  substances,  exist  in  our  food ;  this 
being  the  only  way  in  which  material  is  supplied  for  the  con- 
tinual repair  which  is  characteristic  of  living  tissues.  They 
are  all  introduced  from  without.  Certain  principles,  such  as 
water  and  the  inorganic  salts,  are  merely  transitory  in  the  in- 
terior of  the  body,  and  are  discharged  in  the  same  form  in 


24  INTRODUCTION. 

which  they  enter.  Others  are  consumed  in  the  process  of 
repair,  and  after  having  performed  their  functions,  are  thrown 
off  as  effete  matters.  Examples  of  the  latter  are  fibrin 
and  albumen,  which  are  transformed  first  into  the  sub- 
stance of  the  tissues,  and  then  into  urea,  creatine,  choleste- 
rine,  and  other  excrementitious  matters,  which  are  the  re- 
sult of  the  breaking  down  or  wearing  out  of  the  tissues. 
Finally,  there  are  certain  principles,  the  sugars  and  fats  for 
example,  which  have  an  important  connection  with  the  pro- 
cess of  nutrition,  and  disappear  in  the  system,  but  whose 
transformations  we  have  not  as  yet  been  able  to  follow. 
These,  besides  being  taken  in  as  food,  are  manufactured  by 
certain  organs,  and  appear  de  novo  in  the  economy. 

Division  of  Proximate  Principles. — In  the  division  ol 
proximate  principles,  we  shall  follow,  with  slight  modifica- 
tions, the  classification  of  Robin  and  Verdeil.  With  refer- 
ence solely  to  anatomical  and  physiological  chemistry,  the 
classification  of  these  authors  cannot  be  improved;  but  in 
treating  of  the  whole  subject  of  physiology,  it  will  be  conven- 
ient to  take  up  certain  of  the  elements  in  connection  with  the 
functions  in  which  they  play  an  important  part.  Oxygen 
and  carbonic  acid,  for  example,  will  be  fully  considered  in 
connection  with  respiration  ;  urea  and  cholesterine  with  ex- 
cretion, &c.  Again,  there  are  some  whose  function  is  appa- 
rently of  so  little  importance,  or  so  obscure,  that,  while  they 
may  be  interesting  in  a  chemical  point  of  view,  merely  as 
constituents  of  the  body,  it  is  not  worth  while  to  treat  of 
them  in  connection  with  physiology. 

The  two  great  divisions  of  proximate  principles  which  we 
propose,  comprise : 

FIRST.  Substances  which  enter  into  the  normal  con- 
stitution of  the  organized  tissues,  and  those  constituents  of 
the  fluids  which  are  used  in  nutrition. 


PROXIMATE    PEmCIPLES.  25 

SECOND.  Substances  which  are  the  result  of  the  wearing 
out  of  the  tissues,  and  are  not  used  in  nutrition? 

The  first  division,  which  is  the  only  one  that  will  be  taken 
up  in  this  connection,  may  be  subdivided,  according  to  the 
classification  of  Robin  and  Yerdeil,  into  three  classes. 

1.  Inorganic  Substances. — This  class  is  of  inorganic  ori- 
gin, definite  chemical  composition,  and  crygtallizable.     The 
substances  forming  it  are  all  introduced  from  without,  and  are 
all  discharged  from  the  body  in  the  same  form  in  which  they 
entered.     They  never  exist  alone,  but  are  always  combined 
with  the  organic  principles,  to  form  the  organized  fluids  or 
solids.     This  union  is  "  atom-to-atom,"  and  so  intimate  that 
they  are  taken  up  with  the  organic  elements,  as  the  latter  are 
worn  out  and  become  effete,  and  are  discharged  from  the 
body,  though  themselves  unchanged.     To  supply  the  place 
of  the  principles  thus  thrown  off,-  a  fresh  quantity  is  depos- 
ited in  the  process  of  nutrition.     They  give  to  the  various 
organs  important  properties  ;  and,  though  identical  with  sub- 
stances in  the  inorganic  world,  in  the  interior  of  the  body 
they  behave  as  organic  substances.      They  require  no  special 
preparation  for  absorption,  but  are  soluble  and  taken  in  un- 
changed.    They  are  received  into  the  body  in  about  the  same 
proportion  at  all  periods  of  life,  but  their  discharge  is  nota- 
bly diminished  in  old  age  ;  giving  rise  to  calcareous  incrusta- 
tions and  deposits,  and  a  considerable  increase  in  the  calca- 
reous matter  entering  into  the  composition  of  the  tissues. 
As  examples  of  this  class  we  may  cite  water,  chloride  of  so- 
dium, the  carbonates,  sulphates,  phosphates,  and  other  inor- 
ganic salts. 

2.  Organic  Non-Nitrogenized  Substances. — This  class  of 

1  This  division  is  composed  of  excrementitious  matters,  which  will  be  fully 
considered  when  treating  of  excretion.  It  is  included  in  the  second  class  of  prox- 
imate principles  by  Robin  and  Verclcil. 


26  INTEODUCTION. 

proximate  principles  is  of  organic  origin,  definite  chemical 
composition,  and  crystallizable.  With  the  exception  of  the 
salts  peculiar  to  the  bile,  which  will  be  considered  when  we 
come  to  treat  of  that  fluid,  pneumic  acid,  and  one  or  two 
unimportant  principles,  they  are  distinguished  by  being  com- 
posed of  three  elements,  Carbon,  Hydrogen,  and  Oxygen. 
As  they  thus  contain  hydrogen  and  carbon,  to  the  exclusion 
of  all  other  elements,  except  the  almost  universal  principle, 
oxygen,  they  are  frequently  spoken  of  as  Hydro-carbons. 
They  are  distinguished  from  other  organic  substances  by  the 
absence  of  nitrogen,  which  has  given  them  the  name  of  Non- 
nitrogenized  or  Non-azotized  substances.  They  are  intro- 
duced into  the  body  as  food,  and  are  manufactured  in  the 
economy  by  special  organs  ;  but,  unlike  principles  of  the  first 
class,  with  the  exception  of  sugar  and  fat,  which  are  dis- 
charged in  the  milk  during  lactation,  are  never  discharged 
from  the  body  in  health.  The  principles  of  this  class  play 
an  important  part  in  development  and  nutrition.  One  of 
them,  sugar,  appears  very  early  in  foetal  life,  formed  first  by 
the  placenta,  and  afterwards  by  the  liver ;  its  formation  by 
the  latter  organ  continuing  during  life.  Fat  is  a  necessary 
element  of  food,  and  is  also  formed  in  the  interior  of  the 
body.  The  exact  influence  which  these  substances  have  on 
development  and  nutrition  is  not  known,  but  experiments 
and  observation  have  shown  that  this  influence  is  important. 
Many  physiologists  are  of  the  opinion  that  principles  of  this 
class  undergo  direct  oxidation  or  combustion  in  the  lungs,  and 
have  the  exclusive  office  of  keeping  up  the  animal  tempera- 
ture. At  one  time,  indeed,  they  were  generally  spoken  of  as 
calorific  elements ;  but  in  the  present  condition  of  science  this 
exclusive  view  is  not  tenable ;  and  we  shall  see,  when  treating 
of  the  subject  of  animal  heat,  that  its  production  cannot  be 
referred  entirely  to  combustion  of  the  hydro-carbons.  The 
sugars  and  fats,  lactic  acid  and  the  lactates,  pneumic  acid  and 
the  pneumates,  the  fatty  acids  and  their  combinations,  consti- 
tute the  most  important  principles  of  this  class. 


PKOX1MATE   PRINCIPLES.  27 

3.  Organic  Nitrogenized  Su'bsta/n^ces. — This  class  of  prox- 
imate principles  is  of  organic  origin,  indefinite  chemical  com- 
position, and  non-crystallizable.  Substances  forming  this 
class  are  apparently  the  only  principles  which  are  endowed 
with  vital  properties,  taking  materials  for  their  regeneration 
from  the  nutritive  fluids,  and  appropriating  them  to  form 
part  of  their  own  substance.  Considered  from  this  point 
of  view,  they  are  different  from  any  thing  which  is  met  with 
out  of  the  living  body.  They  are  all,  in  the  body,  in  a  state 
of  continual  change,  wearing  out  and  becoming  effete,  when 
they  are  transformed  into  excrementitious  substances,  which 
constitute  the  second  grand  division  of  proximate  principles. 
The  process  of  repair  in  this  instance  is  not  the  same  as  in 
inorganic  substances,  which  enter  and  are  discharged  from 
the  body  without  undergoing  any  change.  The  analogous 
substances  which  exist  in  food,  undergo  a  very  elaborate  prep- 
aration, by  digestion,  before  they  can  even  be  absorbed  by 
the  blood-vessels ;  and  still  another  change  takes  J)lace 
when  they  are  appropriated  by  the  various  tissues.  They 
exist  in  all  the  solids,  semi-solids,  and  fluids  of  the  body, 
never  alone,  but  always  combined  with  inorganic  substances. 
As  a  peculiarity  of  chemical  constitution,  they  all  contain 
nitrogen,  which  has  given  them  the  name  of  Nitrogenized  or 
Azotized  principles.  As  before  intimated,  they  give  to  the 
tissues  and  fluids  their  vital  properties.  In  studying  their 
properties  more  fully,  we  shall  see  that  they  are  by  far  the 
most  important  elements  in  the  organism.  The  elaborate 
preparation  which  they  require  for  absorption  involves  the 
most  important  part  of  the  function  of  digestion.  Their  ab- 
solute integrity  is  necessary  to  the  operation  of  the  essential 
functions  of  many  tissues,  as  muscular  contraction,  or  con- 
duction of  nervous  force.  An  exact  knowledge  of  all  the 
transformations  which  take  place  in  their  regeneration  and  the 
process  by  which  they  are  converted  into  effete  or  excremen- 
titious matters,  would  enable  us  to  comprehend  nutrition, 
which  is  the  essence  of  physiology  ;  but  as  yet  we  know  little 


28  INTRODUCTION. 

of  these  changes,  and  consider  ourselves  fortunate  in  under- 
standing a  few  of  the  laws  which  regulate  them.  As  exam- 
ples of  principles  of  this  class  we  may  cite  musculine,  os- 
teine,  fibrin,  albumen,  and  caseine. 


INOEGANIC   PRINCIPLES. 

The  number  of  principles  of  this  class,  now  well  estab- 
lished as  existing  in  the  human  body,  is  twenty-one.1  All 
substances  which  at  any  time  exist  in  the  body  are  proximate 
principles ;  but  some  are  found  in  small  quantities,  are  not 
always  present,  and  apparently  have  no  very  important  func- 
tion. These  will  be  passed  over  rapidly,  as  well  as  those 
which  are  so  intimately  connected  with  some  important  func- 
tion as  to  render  their  full  consideration  in  connection  with 
that  function  indispensable.  The  following  is  a  list  of  the 
inorganic  principles,  excluding  those  which  are  excrementi- 
tious,'  and  one  or  two  which  are  not  yet  well  established : 

Table  of  Inorganic  Principles. 

Proximate  Principle.  Where  Found. 

'  Oxygen.  Lungs  and  Blood. 

Hydrogen.  Gases  of  Stomach  and  Colon. 

Nitrogen.  Lungs,  Intestinal  Gases,  and  Blood. 

Carburetted  Hydrogen.  Lungs  (expired  air),  Intestines. 

[_  Sulphuretted  Hydrogen.  Lungs  (expired  air),  Intestines. 

Water.  Universal. 

Chloride  of  Sodium.  Universal,  except  the  enamel. 

Chloride  of  Potassium.  Muscles,  Liver,  Milk,  Chyle,  Blood,  Mu- 

cus, Saliva,   Bile,   Gastric  Juice,  Ce- 
phalo-rachidian  Fluid,  and  Urine. 


1  Robin  and  Verdeil  give  twenty-nine ;  but  of  these,  three  (acid  phosphate  of 
soda,  acid  phosphate  of  lime,  and  ammonio-magnesian  phosphate)  are  found  only 
in  the  urine,  and  may  be  considered  as  coming  under  the  head  of  excrements, 
with  carbonic  acid,  which  is  one  of  the  most  important  excretions ;  one  (bicar- 
bonate of  lime)  is  abnormal ;  one  (bicarbonate  of  potassa)  is  found  only  in  cer- 
tain of  the  inferior  animals ;  and  two  (carbonate  and  bicarbonate  of  ammonia) 
are  doubtful. 


INOKGANIC  PRINCIPLES. — GASES. 


29 


Proximate  Principle. 
Phosphate  of  Lime  (basic). 
Carbonate  of  Lime. 


Carbonate  of  Soda. 

Carbonate  of  Potassa. 
Phosphate  of  Magnesia. 
Phosphate  of  Soda  (neutral). 
Phosphate  of  Potassa. 
Sulphate  of  Soda. 

Sulphate  of  Potassa. 
Sulphate  of  Lime. 
Hydrochlorate  of  Ammonia. 
Carbonate  of  Magnesia. 


Bicarbonate  of  Soda. 


Where  Found. 

Universal. 

Bones,  Teeth,  Cartilage,  Internal  Ear, 
Blood,  Sebaceous  Matter,  and  some- 
times Urine. 

Blood,  Bone,  Saliva,  Lymph,  Cepholo- 
rachidian  Fluid,  and  Urine. 

Blood,  Bone,  Lymph,  and  Urine. 

Universal. 

Universal. 

Universal. 

Universal,  except  Milk,  Bile,  and  Gastric 
Juice. 

Same  as  Sulphate  of  Soda. 

Blood  and  Feces. 

Gastric  Juice,  Saliva,  Tears,  and  Urine. 

A  trace  in  the  Blood  and  Sebaceous 
matter. 

Blood  (Liebig). 


The  Gases. 


The  gases  (oxygen,  hydrogen,  nitrogen,  carburetted  hy- 
drogen, sulphuretted  hydrogen)  1  exist  both  in  a  gaseous  state, 
and  in  solution  in  some  of  the  fluids  of  the  body.  Oxygen 
plays  a  most  important  part  in  the  function  of  respiration  ; 
but  the  office  of  the  others  is  by  no  means  so  essential.  Ni- 
trogen seems  to  be  formed  by  the  system  in  small  quantity,  is 
taken  up  by  the  blood  and  exhaled  by  the  lungs ;  except  dur- 
ing inanition,  when  the  blood  absorbs  a  little  from  the  in- 
spired air.  It  exists  in  greatest  quantity  in  the  intestinal 
canal.  The  carburetted  and  sulphuretted  hydrogen,  with 
pure  hydrogen,  are  found  in  minute  quantities  in  the  expired 
air,  and  are  also  found  in  a  gaseous  state  in  the  alimentary 
canal.  From  the  offensive  nature  of  the  contents  of  the 
large  intestine,  we  would  suspect  the  presence  of  sulphuretted 
hydrogen  in  considerable  quantity ;  but  actual  analysis  has 
shown  that  the  gas  contained  in  the  stomach  and  intestines, 


1  Carbonic  acid  is  here  omitted,  and  will  be  treated  of  under  the  head  of  res- 
piration. 


30  INTRODUCTION. 

large  as  well  as  small,  is  composed  chiefly  of  nitrogen,  with 
hydrogen  and  carburetted  hydrogen  in  about  equal  propor- 
tion, five  to  eleven  parts  per  hundred,  and  but  a  trace  of  sul- 
phuretted hydrogen.  With  the  exception  then  of  oxygen 
and  carbonic  acid,  the  latter  being  an  excretion,  the  gases  do 
not  hold  an  important  place  among  the  proximate  principles. 
At  all  events,  their  function,  whether  it  be  important  or  not, 
is  but  little  understood. 

Water,  HO. 

"Water  is  by  far  the  most  important  of  the  inorganic  prin- 
ciples.1 It  is  present  at  all  periods  of  life,  existing  even  in 
the  ovum.  It  exists  in  all  parts  of  the  body ;  in  the  fluids, 
some  of  which,  as  the  lachrymal  fluid  and  perspiration,  con- 
tain little  else,  and  in  the  hardest  structures,  as  the  bones,  or 
the  enamel  of  the  teeth. 

In  the  solids  and  semi-solids  it  does  not  exist  as  water, 
but  enters  into  their  structure,  assuming  the  consistence 
by  which  they  are  characterized.  For  example,  we  have 
water  in  the  bones,  teeth,  and  even  in  the  enamel,  not  con- 
tained in  the  interstices  of  their  structure,  as  in  a  sponge, 
but  incorporated  into  the  substance  of  the  tissue.  In  these 
situations  it  is  essentially  water  of  composition.  During  the 
process  of  nutrition,  water  is  deposited  in  the  tissues  with  the 
other  nutritive  principles,  as  we  have  it  incorporated  in  the 
substance  of  certain  inorganic  compounds  in  the  process  of 
crystallization,  when  it  is  known  in  chemistry  as  water  of 
crystallisation.  In  the  interior  of  the  body,  water  is  thus 
incorporated  in  the  substance  of  organic  matters,  which  are 

1  In  comparing  principles  which  are  essential  to  nutrition  and  to  life,  it  is  im- 
possible to  say  that  one  is  absolutely  more  important  than  another ;  still,  writers 
are  in  the  habit  of  making  a  distinction  in  the  importance  of  necessary  constit- 
uents of  the  body,  chiefly  with  reference  to  their  quantity  and  the  extent  of  their 
distribution.  When  we  come  to  organic  principles,  we  shall  see  that  these  are 
manifestly  the  most  important  constituents  of  the  living  body,  as  giving  to  the 
tissues  their  vital  properties. 


WATER.  31 

of  indefinite  chemical  composition,  and  non-crystallizal)le, 
and  we  have  no  reason  to  be  surprised,  as  physiologists,  to 
find  it  entering  into  their  composition  in  indefinite  propor- 
tions, assuming  the  form  and  consistence  of  the  organic  sub- 
stance. Our  definition  of  a  proximate  principle  is :  "  a  sub- 
stance extracted  from  the  body,  which  cannot  be  further 
subdivided  without  chemical  decomposition,"  The  union 
of  water  with  the  organic  principles  is  chemical ;  and  though 
feeble,  is  not  more  so  than  the  chemical  union  of  elements 
in  some  compounds  found  in  the  inorganic  world.  The  bi- 
carbonates,  for  example,  are  formed  by  a  union  of  two  equiv- 
alents of  carbonic  acid  with  one  of  the  base ;  but  the  second 
atom  of  carbonic  acid  is  in  so  feeble  a  condition  of  union,  that 
it  is  set  free  when  the  compound  is  placed  under  the  receiver 
of  an  air-pump.  It  might  be  objected  that  water  is  combined 
with  organic  substances  in  an  indefinite  quantity,  while  the 
carbonic  acid  is  present  in  definite  proportion ;  but  it  must  be 
remembered  that  indefinite  proportions  of  all  the  constituents 
are  characteristic  of  organic  substances ;  and  that  the  quantity 
of  water  existing,  within  certain  limits,  in  indefinite  propor- 
tions, only  obeys  the  law  which  regulates  the  components 
which  are  universally  recognized  as  existing  in  a  state  of 
chemical  union.  The  only  difference  between  water  and  the 
other  constituents  of  an  organic  compound,  is  that  the  former 
is  extracted  with  facility ;  as  one  atom  of  carbonic  acid  is 
extracted  from  the  bicarbonates  more  easily  than  the  other. 
Studying  the  organism  as  physiologists,  we  must  consider 
water  as  an  integral  constituent  of  the  tissues,  and  not  as 
merely  absorbed  by  them. 

All  the  organized  structures  contain  a  certain  proportion  of 
water,  and  this  is  necessary  to  the  performance  of  all  or  any  of 
their  functions.  If  a  normal  muscle  be  considered  as  a  con- 
tracting organ,  and  a  nerve  as  a  conducting  organ,  or  albu- 
men as  a  nutritious  element,  we  must  consider,  as  one  of  their 
constituents,  water.  It  is  necessary  to  the  proper  form,  consist- 
ence, and  function  of  these  and  all  organized  structures.  In 
analysis  of  organic  matters,  when  water  is  lost  or  driven  off 


32  INTRODUCTION. 

in  our  manipulations,  the  principle  is  not  brought  near  a  state 
of  chemical  purity,  but  is  essentially  and  radically  changed. 

The  quantity  of  water  which  each  organic  substance  con- 
tains is  important  /  and  it  is  provided  that  this  quantity, 
though  indefinite,  shall  not  exceed  or  fall  below  certain  lim- 
its. The  truth  of  this  proposition  is  made  evident  from  the 
following  facts :  In  the  first  place,  all  organs  and  tissues  must 
contain  a  tolerably  definite  quantity  of  water  to  give  them 
proper  consistence.  The  evils  of  too  great  a  proportion  of 
water  in  the  system,  and  consequently  a  diminution  of  solid 
elements,  are  well  known  to  the  practical  physician.  Gen- 
eral muscular  debility,  loss  of  appetite,  dropsies,  and  various 
other  indications  of  imperfect  nutrition,  are  among  the  re- 
sults of  such  a  condition ;  while  a  deficiency  of  water  is  im- 
mediately made  known  by  the  sensation  of  thirst,  which 
leads  to  its  introduction  from  without. 

The  fact  that  water  never  exists  in  any  of  the  fluids,  semi- 
solids,  or  solids,  without  being  combined  with  inorganic  salts, 
and  especially  chloride  of  sodium,  is  one  reason  why  its  pro- 
portion in  various  situations  is  to  a  certain  extent  constant. 
The  presence  of  these  salts  influences,  in  the  semi-solids  at 
least,  the  quantity  of  water  entering  into  their  composition, 
and  consequently  regulates  their  consistence.  A  very  simple 
experiment  shows  this  with  reference  to  the  chloride  of 
sodium.  If  a  piece  of  muscle  be  placed  in  a  strong  solution 
of  common  salt,  as  in  salting  meat,  it  becomes  harder,  and 
loses  a  portion  of  its  water  of  composition ;  while  exposed 
to  the  action  of  pure  water,  it  absorbs  a  certain  quantity  and 
becomes  softer.  The  nutrient  fluid  of  the  muscles  during 
life  contaiiiS  water  with  just  enough  saline  matter  to  pre- 
serve their  normal  consistence.  This  action  of  saline  matters 
is  even  more  apparent  in  the  case  of  the  blood  corpuscles. 
If  pure  water  be  added  to  the  blood,  these  bodies  swell  up 
and  are  finally  dissolved ;  while  if  we  add  a  strong  solu- 
tion of  salt,  they  lose  water,  and  become  shrunken  and 
corrugated ;  but  their  natural  form  and  consistence  can 
be  restored,  even  after  they  have  been  completely  dried,  by 


WATEE.  33 

adding  water  containing  -about  the  proportion  of  salt  which 
exists  in  the  plasma. 

It  seems  clear,  then,  that  water  is  a  necessary  element  of 
all  tissues,  and  is  especially  important  to  the  proper  constitu- 
tion of  organic  nitrogenized  substances ;  that  it  enters  into 
the  constitution  of  these  substances,  not  as  pure  water,  but 
always  in  connection  with  certain  inorganic  salts ;  that  its 
proportion  is  confined  within  certain  limits ;  and  that  the 
quantity  in  which  it  exists,  in  organic  nitrogenized  substances 
particularly,  is  regulated  by  the  quantity  of  salts  which  en- 
ter, with  it,  into  the  constitution  of  these  substances. 

The  quantities  of  water  which  can  be  driven  off  by  a  mod- 
erate temperature  (212°  Fahr.)  from  the  different  fluids  and 
tissues  of  the  body,  vary  of  course  very  considerably,  ac- 
cording to  the  consistence  of  the  parts.  The  following  is  a 
list  of  the  quantities  in  the  most  important  fluids  and  solids : 

Table  of  Quantity  of  Water. 

Parts  per  1,000. 
In  Enamel  of  the  Teeth. .  2 


1 

a 


Epithelial  Desquamation 37 

Teeth 100 

Bones 130 

'    Tendons  (Burdach) 500 

Articular  Cartilages 550 

Skin  (AVeinholt) 575 

Liver  (Frommherz  and  Gugert) 618 

Muscles  of  Man  (Bibra) 725 

Ligaments  (Chevreul) 768 

Mean  of  Blood  of  Man  (Becquerel  and  Rodier) 780 

"  Milk  of  Human  Female  (Simon) 887 

"  Chyle  of  Man  (Rees) 904 

"  Bile 905 

"  Urine 933 

"  Human  Lymph  (Tiedemann  and  Gmelin) 960 

"  Human  Saliva  (Mitscherlich) 983 

"  Gastric  Juice 984 

"  Perspiration 986 

"  Tears 990 

"  Pulmonary  Vapor 997 

1  This  table  is  made  of  selections  from  the  table  of  Robin  and  Verdeil — taken 
from  various  authors. 
3 


34  INTRODUCTION. 

Function  of  Water. — After  what  has  been  stated  re- 
specting the  condition  in  which  water  exists  in  the  body, 
there  remains  but  little  to  say  concerning  its  function.  As 
a  constituent  of  organized  tissues,  it  gives  to  cartilage  its 
elasticity,  to  tendons  their  pliability  and  toughness ;  it  is 
necessary  to  the  peculiar  pow^r  of  resistance  of  the  bones, 
and,  as  we  have  already  seen,  it  is  necessary  to  the  proper 
consistence  of  all  parts  of  the  body.  It  has  other  important 
functions  as  a  solvent.  Soluble  articles  of  food  are  intro- 
duced in  solution  in  water.  The  excrementitious  matters, 
which  are  generally  soluble  in  water,  are  dissolved  by  it  in 
the  blood,  carried  to  the  organs  of  excretion,  and  discharged 
in  a  watery  solution  from  the  body. 

Origin  and  Discharge  of  Water. — It  is  evident  that  the 
great  proportion  of  water  is  introduced  from  without  in  the 
fluids,  and  in  the  watery  constituents  of  all  kinds  of  food ; 
but  the  theoretical  views  of  some  physiologists  with  regard 
to  the  hydrocarbons  and  their  combustion,  led  to  the  supposi- 
tion that  water  is  also  formed  in  the  body  by  a  direct  union 
of  oxygen  and  hydrogen.  The  true  way  of  determining  this 
point  is  to  estimate  all  the  water  introduced  into  the  organism, 
and  compare  this  quantity  with  that  which  is  discharged.  The 
latter  estimate,  however,  presents  very  great  difficulties.  As 
water  is  continually  given  off  in  the  form  of  vapor  from  the 
skin,  and  in  the  expired  air,  the  quantities  thus  discharged 
are  subject  to  great  variations,  dependent  upon  exercise,  tem- 
perature, the  state  of  the  atmosphere,  etc.,  and  even  if  con- 
stant could  be  estimated  with  great  difficulty.  Experiments 
on  this  point  have  been  undertaken  by  Sanctorius,  Barral, 
Boussingault,  and  others;  but  they  are  not  sufficiently  com- 
plete to  settle  the  question. 

In  the  present  state  of  our  knowledge,  we  can  only  say 
that  water  is  introduced  with  the  fluid  and  solid  elements  of 
food,  by  the  stomach,  and  that  it  escapes  by  the  urine,  feces, 
lungs,  and  skin.  There  is  no  direct  evidence  that  any  is  pro- 


CHLORIDE   OF   SODIUM.  oO 

duced  in  the  interior  of  the  body.  In  the  issue  of  water  by 
the  kidneys  and  skin,  it  has  long  been  observed  that,  in  point 
of  activity,  these  two  ermmctories  bear  a  certain  relation  to 
each  other.  When  the  skin  is  inactive,  as  in  cold  weather, 
the  kidneys  discharge  a  large  quantity  of  water ;  when  the 
skin  is  active,  the  quantity  of  water  discharged  by  the  kid- 
neys is  diminished.  Certain  therapeutical  agents,  also,  can 
be  made  to  act  as  diaphoretics  by  combining  other  measures 
which  favor  cutaneous  action  ;  or  as  diuretics,  by  employing 
measures  to  diminish  the  action  of  the  skin. 

Chloride  of  Sodium  (Common  Salt),  !N"aCl. 

Chloride  of  sodium  is  next  in  importance,  as  an  inorganic 
proximate  principle,  to  water.  It  is  found  in  the  body  at  all 
periods  of  life,  existing,  like  water,  in  the  ovum.  It  exists  in  all 
the  fluids  and  solids  of  the  body,  with  the  single  exception  of 
the  enamel  of  the  teeth.  In  the  fluids,  it  seems  to  be  simply 
in  a  state  of  solution,  and  can  be  recognized  by  the  ordinary 
tests ;  in  this  respect  we  may  class  together  the  chlorides  of 
sodium  and  potassium. 

The  quantity  of  chloride  of  sodium  in  the  entire  body 
has  never  been  estimated ;  nor,  indeed,  has  any  accurate  esti- 
mate been  made  of  the  quantity  contained  in  the  various  tis- 
sues ;  for  all  the  chlorides  are  generally  estimated  together. 
It  exists  in  greatest  proportion  in  the  fluids,  giving  to  some 
of  them,  as  the  tears  and  perspiration,  a  distinctly  saline 
taste.  The  following  table  gives  an  idea  of  the  quantity 
which  has  been  found  in  some  of  the  most  important  of  the 
fluids  and  solids : 

Table  of  Quantity  of  Chloride  of  Sodium. 

Parts  per  1,000. 

In  Blood,  Human  (Lehmann) 4-210 

"  Chyle  (Lehmann) 6-310 

"  Lymph  (Nasse) 4-120 

"  Milk,  Human  (Lehmann) 0-870 


36  INTRODUCTION. 

Parts  per  1,000. 

In  Saliva,  Human  (Lehmann) 1-530 

"  Perspiration,  Human  (mean  of  three  analyses,  Piutti). . . .  3-433 

"  Urine  (maximum)  \  (  7'280 

"      "      (medium)..  [•  Valentin.  •<   4.610 

"      "      (minimum))  (  2-400 

"  Fecal  Matters  (Berzelius) 3-010 

• 

Function  of  Chloride  of  Sodium. — The  function  of  this 
principle  is  undoubtedly  important,  but  is  not  yet  fully  un- 
derstood. It  does  not  seem  to  enter  into  the  substance  of 
the  organized  solids  and  semi-solids  as  an  important  and  es- 
sential element,  but  apparently  exercises  its  chief  function  in 
the  fluids.  It  certainly  determines,  to  a  great  extent,  the 
quantities  of  exudations,  regulates  absorption,  and  serves  to 
maintain  the  albuminoids,  especially  those  contained  in  the 
blood,  in  a  state  of  fluidity.  Albumen  is  coagulated  by  heat 
with  much  greater  difficulty  in  a  solution  of  chloride  of  so- 
dium than  when  mixed  with  pure  water.  A  strong  solution 
of  common  salt  is  capable  of  dissolving  casein,  or  of  prevent- 
ing the  coagulation  of  fibrin.  We  have  already  alluded  to 
the  fact  that  it  is  the  chloride  of  sodium  particularly  which 
regulates  the  quantity  of  water  entering  into  the  composition 
of  the  blood  corpuscles,  thereby  preserving  their  form  and 
consistence ;  and  that  it  seems  to  perform  an  analogous  func- 
tion with  reference  to  the  other  semi-solids  of  the  body. 
"With  regard  to  the  general  function  of  this  substance,  the 
following  proposition  of  Liebig  is  adopted  by  Robin  and  Yer- 
deil,  and  a  little  reflection  will  show  that  it  is  sustained,  as 
far  as  we  know,  by  the  facts : 

"  Common  salt  is  intermediate  in  certain  general  pro- 
cesses^ and  does  not  participate  ~by  its  elements  in  the  forma- 
tion of  organs" 

In  the  first  place,  the  fluids  of  the  body  are  generally  in- 
termediate in  their  functions,  containing  nutritious  elements, 
which  are  destined  to  be  appropriated  by  the  tissues  and  organs, 
and  worn-out  elements,  which  are  to  be  separated  from  the  body. 
In  the  blood  and  chyle  chloride  of  sodium  is  found  in  greatest 


CHLORIDE   OF   SODIUM.  37 

abundance.  When  the  nutrition  of  organs  takes  place,  which 
consists  in  the  fixation  of  new  proximate  principles,  chloride 
of  sodium  is  not  deposited  in  any  considerable  quantity,  but 
seems  to  regulate  the  general  process,  at  least  to  a  certain 
extent.  In  all  civilized  countries  salt  is  used  extensively  as 
a  condiment,  and  it  undoubtedly  facilitates  digestion  by  ren- 
dering the  food  more  savory,  and  increasing  the  flow  of  the 
digestive  fluids  ;  here,  likewise,  acting  simply  as  an  interme- 
diate agent.  There  is  nothing  more  general  among  men  and 
animals  than  this  desire  for  common  salt.  The  carnivora 
crave  it,  and  obtain  it  in  the  blood  of  animals  ;  the  herbivora 
frequent  "  salt  licks  "  and  places  where  it  is  found,  and  relish 
it  when  mixed  with  their  food ;  while  by  man  its  use  is 
almost  universal.  In  the  domestic  herbivora  the  effect  of 
a  deprivation  of  this  article  is  very  marked,  and  has  been 
made  the  subject  of  some  very  interesting  experiments  by 
Boussingault.  This  observer  experimented  upon  two  lots 
of  bullocks,  of  three  each,  all  of  them,  at  the  time  the  ob- 
servations were  commenced,  being  perfectly  healthy  and  in 
fine  condition.  One  of  these  lots  he  deprived  entirely  of  salt, 
excepting  what  was  contained  in  their  fodder,  while  the  other 
was  supplied  with  the  usual  quantity.  No  marked  difference 
in  the  two  lots  was  noticed  until  between  five  and  six  months, 
when  the  difference  in  general  appearance  was  very  distinct. 
The  animals  receiving  salt  retained  their  fine  appearance, 
while  the  others,  though  not  diminished  in  flesh,  were  not  as 
sleek  and  fine.  At  the  end  of  a  year  the  difference  was  very 
marked.  The  hides  of  those  which  had  been  deprived  of  salt 
were  rough  and  ragged,  their  appearance  listless  and  inani- 
mate, contrasting  strongly  with  the  sleek  appearance  and 
vivacious  disposition  of  the  others.1  The  experiments  of 
Boussingault  are  the  most  conclusive  that  have  ever  been 
instituted  with  regard  to  the  influence  of  chloride  of  sodium 

1  BOUSSINGAULT,  Memoir es  de  Chimie  Agricole  et  de  Physiologie,  Paris,  1854, 
p.  271  et  seq. 


38  INTRODUCTION. 

upon  nutrition.  They  indicate  a  certain  deficiency  in  the 
nutrition  of  animals  deprived  of  it,  but  not  any  considerable 
loss  of  weight.  Before  these  observations  were  made,  Dailly 
made  upon  twenty  sheep  analogous  experiments,  which  were 
continued  for  three  months.  At  the  end  of  that  time  the 
lot  which  received  salt  presented  a  considerable  excess  of 
weight  (about  22f  Ibs.)  over  the  others.1 

It  is  a  significant  fact  that  the  quantity  of  chloride  of  so- 
dium existing  in  the  blood  is  not  subject  to  variation,  but 
that  an  excess  introduced  with  the  food  is  thrown  off  by  the 
kidneys.  The  quantity  in  the  urine,  then,  bears  a  relation  to 
the  quantity  introduced  as  food,  but  the  proportion  in  the 
blood  is  constant.  This  is  another  fact  in  favor  of  the  view 
that  the  presence  of  a  definite  quantity  of  common  salt  in 
the  circulating  fluid  is  essential  to  the  proper  performance  of 
the  general  function  of  nutrition. 

Origin  and  Discharge  of  Chloride  of  /Sodium. — This 
substance  is  always  introduced  with  food  in  the  condition 
in  which  it  is  found  in  the  body.  It  is  contained  in  the  sub- 
stance of  all  kinds  of  food,  animal  and  vegetable ;  but  in  the 
herbivora  and  in  man,  this  source  is  not  sufficient  to  supply 
the  wants  of  the  system,  and  it  is  introduced,  therefore,  as 
salt.  The  quantity  which  is  discharged  from  the  body  has 
been  estimated  by  Barral2  to  be  somewhat  less  than  the 
quantity  introduced,  about  one-fifth  disappearing ;  but  these 
estimates  are  not  exactly  accurate,  for  the  amount  thrown  off 
in  perspiration  has  never  been  directly  ascertained.  It  exists 
in  the  blood  in  connection  with  the  phosphate  of  potassa,  and 
a  certain  amount  is  lost  in  a  double  decomposition  which 
takes  place  between  these  two  salts,  resulting  in  the  forma- 
tion of  chloride  of  potassium  and  phosphate  of  soda.  It  also 
is  supposed  to  furnish  the  soda  to  all  the  salts  which  have  a 

1  LONGET,  Traite  de  Physiologic,  tome  i.,  p.  76. 

2  Cited  by  KOBIN  and  YERDEIL.     Chimie  Anatomique  et  Physiologique,  Paris, 
1853,  tome  ii.,  p.  193. 


CHLOEIDE   OF  POTASSIUM.  39 

soda  base,  and  a  certain  quantity,  therefore,  disappears  in  this 
way. 

Existing,  as  it  does,  in  all  the  solids  and  fluids  of  the 
body,  it  is  discharged  in  all  the  excretions,  being  thrown  off 
in  the  urine,  feces,  perspiration,  and  mucus. 

Chloride  of  Potassium,  KC1. 

Chloride  of  potassium,  though  not  as  important  a  proxi- 
mate principle  as  the  chloride  of  sodium,  nor  so  generally 
distributed  in  the  economy,  seems  to  have  an  analogous 
function.  It  is  found  in  the  Muscles,  Liver,  Milk,  Chyle, 
Blood,  Mucus,  Saliva,  Bile,  Gastric  Juice,  Cephalo-Rachidian 
Fluid,  and  Urine.  It  is  exceedingly  soluble,  and  in  these 
situations  exists  in  solution  in  the  fluids. 

Its  quantity  in  these  situations  has  not  been  accurately 
ascertained,  as  it  has  generally  been  estimated  together  with 
the  chloride  of  sodium.  In  the  muscles,  it  exists,  however, 
in  a  larger  proportion  than  common  salt.  In  cow's  milk, 
Berzelins 1  has  found  1'7  pts.  per  1,000 ;  Pfaff  and  Schwartz, 
1*35  per  1,000  in  cow's  milk,  and  0*3  per  1,000  in  human 
milk.2 

Of  the  function  of  this  principle,  little  remains  to  be  said 
after  what  has  been  stated  with  regard  to  the  chloride  of 
sodium.  Their  functions  are  probably  identical,  though  the 
latter,  from  its  greater  quantity  in  the  fluids,  and  its  univer- 
sal distribution,  is  by  far  the  more  important. 

Origin  and  Discharge  of  Chloride  of  Potassium. — This 
substance  has  two  sources ;  one  in  the  food,  existing,  as  it 
does,  in  muscular  tissue,  milk,  etc.,  and  the  other  in  a  chem- 
ical reaction  between  the  phosphate  of  potassa  and  the 
chloride  of  sodium,  forming  the  chloride  of  potassium  and 


1  SIMON,  Chemistry  of  Man,  American  edit.,  p.  342. 

2  ROBIN  and  YERDEIL,  op.  cit.,  tome  ii.,  p.  205. 


40  INTRODUCTION. 

the  phosphate  of  soda.  That  this  decomposition  takes  place 
in  the  body,  is  evident  from  the  fact  that  the  ingestion  of  a 
considerable  quantity  of  common  salt  has  been  found,  in  the 
sheep,  to  increase  the  quantity  of  chloride  of  potassium  in 
the  urine,  without  having  any  influence  on  the  amount  of 
chloride  of  sodium.  The  chloride  of  potassium  is  discharged 
from  the  body  in  the  urine  and  mucus. 

Phosphate  of  Lime,  3  CaO,  PO6. 

Phosphate  of  Lirne  is  found  in  all  the  solids  and  fluids  of 
the  body.  As  it  is  always  united,  in  the  solids,  with  organic 
substances  as  an  important  element  of  constitution,  it  is 
hardly  second  in  importance  to  water.  It  differs  in  its  func- 
tions so  essentially  from  the  chlorides  of  sodium  and  potas- 
sium, that  they  are  hardly  to  be  compared.  It  is  insoluble 
in  water,  but  held  in  solution  in  the  fluids  of  the  body  by 
virtue  of  free  carbonic  acid,  the  bicarbonates,  and  the  chlo- 
ride of  sodium.  In  the  solids  and  semi-solids,  the  condition 
of  its  existence  is  the  same  as  that  of  water ;  i.  e.  it  is  incor- 
porated, particle  to  particle,  with  the  organic  substance  char- 
acteristic of  the  tissue,  and  is  one  of  its  essential  elements 
of  composition.  Nothing  need  be  added  here  as  to  this  mode 
of  union  in  the  body  of  organic  and  inorganic  substances, 
after  what  has  been  said  under  the  head  of  water. 

The  following  table 1  gives  the  relative  quantity  of  phos- 
phate of  lime  in  various  situations : 

Table  of  Quantity  of  Phosphate  of  Lime. 

Parts  per  1,000. 

In  Arterial  Blood,  )  p      iale  and  March&1  ( 0-790 

"  Venous  Blood,  )  ( 0-760 

"  Milk,  Human  (Pfaff  and  Schwartz) 2-500 

"  Saliva  (Wright) O'GOO 


1  Selections  from  the  table  of  Robin  and  Verdeil,  op.  cit. 


PHOSPHATE   OF  LIME.  41 

Parts  per  1,000. 

In  Urine  (proportion  to  weight  of  ash,  Fleitmann) 25*700 

"  Excrements  (Berzelius) 40'000 

"  Bone  (Lassaigne) 400- 

Vertebra  of  a  rachitic  patient  (Bostock) 136' 

Teeth  of  Infant  one  day  old.  ^|  C 510- 

Teeth  of  Adult 610- 

Teeth,  at  eighty-one  years..    fLagsaignej    6fi(). 

Enamel  of  Teeth I  I    885' 

By  this  table  it  is  seen  that  the  phosphate  of  lime  exists  in 
very  small  quantity  in  the  fluids,  but  is  abundant  in  the 
solids.  In  the  latter  the  quantity  is  in  proportion  to  the 
hardness  of  the  structure,  the  quantity  in  enamel  being, 
for  example,  more  than  twice  that  in  bone.  The  variations 
in  quantity  with  age  are  very  considerable.  In  the  teeth 
of  an  infant  one  day  old,  Lassaigne  found  510  parts  per 
1,000;  in  the  teeth  of  an  adult,  610  parts;  and  in  the  teeth 
of  an  old  man  of  eighty-one  years,  660  parts.  This  increase 
in  the  calcareous  elements  of  the  bones,  teeth,  etc.,  in  old  age 

j  /  j  o 

is  very  marked ;  and  in  extreme  old  age  they  are  deposited  in 
considerable  quantity  in  situations  where  there  existed  but  a 
small  proportion  in  adult  life.  The  system  seems  to  grad- 
ually lose  the  property  of  appropriating  to  itself  organic  mat- 
ters ;  and  though  articles  of  food  are  digested  as  well  as  ever, 
the  power  of  assimilation  by  the  tissues  is  diminished.  The 
bones  become  brittle,  and  fractures,  therefore,  are  common  at 
this  period  of  life,  when  dislocations  are  almost  unknown. 
Inasmuch  as  the  real  efficiency  of  organs  depends  on  organic 
matters,  the  system  actually  wears  out,  and  this  progressive 
change  finally  unfits  the  various  parts  for  the  performance  of 
their  functions.  An  individual,  if  he  escapes  accidents  and 
dies,  as  we  term  it,  of  old  age,  passes  away  thus  by  a  simple 
wearing  out  of  his  organism. 

function  of  Phosphate  of  Lime. — This  substance,  as  be- 
fore remarked,  enters  largely  into  the  constitution  of  the 
solids  of  the  body.  In  the  bones  its  function  is  most  appa- 


42  INTRODUCTION. 

rent.  Its  existence,  in  suitable  proportion,  is  necessary  to  the 
mechanical  office  of  these  parts,  giving  them  their  power  of 
resistance,  without  rendering  them  too  brittle.  It  is  more 
abundant  in  the  bones  of  the  lower  extremities,  which 
have  to  sustain  the  weight  of  the  body,  than  in  those  of  the 
upper  extremities ;  and  in  the  ribs,  which  are  elastic  rather 
than  resisting,  it  exists  in  less  quantity  than  in  the  bones  of 
the  arm. 

The  necessity  of  a  proper  proportion  of  phosphate  of  lime 
in  the  bones  is  made  evident  by  cases  of  disease.  In  rachi- 
tis, where,  as  is  seen  by  the  table,  its  quantity  is  very  much 
diminished,  the  bones  are  unable  to  sustain  the  weight  of  the 
body,  and  become  deformed.  Finally,  when  the  phosphate  of 
lime  is  deposited,  they  retain  their  distorted  shape.  The 
phosphate  of  lime  may  be  extracted  from  the  bones  by  ma- 
ceration in  dilute  hydrochloric  acid,. which  dissolves  it,  leav- 
ing only  the  organic  substance.  Bones  treated  in  this  way, 
though  they  retain  their  form,  become  very  pliable ;  and  a 
long  slender  one,  like  the  fibula,  may  be  actually  tied  into 
a  knot. 

Origin  and  Discharge  of  Phosphate  of  Lime. — The  ori- 
gin of  this  principle  is  exclusively  from  the  external  world. 
It  enters  into  the  constitution  of  our  food,  and  is  discharged 
with  the  feces,  urine,  and  other  matters  thrown  off  by  the 
body.  Its  quantity  in  the  urine  is  exceedingly  variable.  Le- 
canu  found  from  O437  to  29*250  grains  thrown  off  by  the 
kidneys  during  the  twenty-four  hours.1 

Carbonate  of  Lime,  CaO,  CO2. 

Carbonate  of  lime  exists  in  the  Bones,  Teeth,  Cartilage,  In- 
ternal Ear,  Blood,  Sebaceous  Matter,  and  sometimes  in  the 
Urine.  It  exists  as  a  normal  constituent  in  the  urine  of  some 
herbivora,  but  not  in  the  carnivora,  nor  in  man.  It  is  most 

1  LEHMANN,  Physiological  Chemistry,  American  Edition,  vol.  ii.,  p.  161. 


CARBONATE   OF   LIME.  4:3 

appropriately  considered  immediately  after  the  phosphate  of 
lime,  because  it  is  the  salt  next  in  importance  in  the  consti- 
tution of  the  bones  and  teeth.  In  these  structures  it  exists 
intimately  combined  with  the  organic  matter,  under  the  same 
conditions  as  the  phosphates,  and  has  analogous  functions. 
In  the  fluids  it  exists  in  small  quantity,  and  is  held  in  solu- 
tion by  virtue  of  free  carbonic  acid  and  the  chloride  of  po- 
tassium. 

The  carbonate  of  lime  is  the  only  example  of  an  inor- 
ganic proximate  principle  existing  uncombined,  and  in  a 
crystalline  form,  in  the  body.  In  the  internal  ear  it  is  found 
in  this  form,  and  has  a  function  connected  with  audition. 

According  to  Robin  and  Verdeil,  it  is  possible  that  in 
chemical  analyses  a  certain  quantity  may  come  from  a 
decomposition  by  calcination  of  those  salts  of  lime  which 
contain  a  combustible  acid.1  These  authors  give  a  table 
of  the  quantity  of  this  substance  in  various  of  the  solids 
and  fluids  of  the  body,  from  which  we  make  the  following 
selections : 

Table  of  Quantity  of  Carbonate  of  Lime. 

Parts  per  1,000. 

In  Bone,  Human  (Berzelius) 113-00 

"     "            "      (Marchand) 102-00 

"     "            "      (Lassalgne) 76-00 

"  Teeth  of  Infant  one  day  old \                   t  ...  140*00 

"  Teeth  of  Adult j-  Lassaigne  )  . . .  100-00 

"  Teeth  of  Old  Man,  eighty-one  years  )                   (,. . .  lO'OO 

"  Urine  of  Horse  (Boussingault). 10-82 

Origin  and  Discharge  of  Carbonate  of  Lime. — Carbonate 
of  lime  is  introduced  into  the  body  with  our  food,  held  in  so- 
lution in  water  by  the  carbonic  acid,  Which  is  always  present 
in  small  quantity.  It  is  also  formed  in  the  body,  particularly 
in  the  herbivora,  by  a  decomposition  of  the  tartrates,  ma- 

1  Op.  cifc,  vol.  ii.,  p.  247. 


44:  INTRODUCTION. 

lates,  citrates,  and  acetates  of  lime  contained  in  the  food. 
These  salts,  meeting  with  carbonic  acid,  are  decomposed,  and 
the  carbonate  of  lime  is  formed.  It  is  probable  that  in  the 
human  subject  some  of  it  is  changed  into  the  phosphate  of 
lime,  and  in  this  form  is  discharged  in  the  urine  ;  but  when 
and  how  this  change  takes  pla^e  has  not  been  definitely  as- 
certained. 

Carbonate  of  Soda,  NaO,  CO2  +  10  HO. 

Carbonate  of  soda  is  found  in  the  blood  and  saliva,  giv- 
ing to  these  fluids  their  alkalinity  ;  in  the  urine  of  the  hu- 
man subject,  when  it  is  alkaline  without  being  ammoniacal ; 
in  the  urine  of  the  herbivora ;  in  the  lymph,  cephalo-rachid- 
ian  fluid,  and  bone.  The  analyses  of  chemists  with  regard 
to  this  substance  are  very  contradictory,  on  account  of  its 
formation  during  the  process  of  incineration  ;  but  there  is  no 
doubt  that  it  is  found  in  the  above  situations.  The  follow- 
ing table  gives  the  quantities  which  have  been  found  in  some 
of  the  fluids  and  solids : 

Table  of  Quantity  of  Carbonate  of  Soda. 

Parts  per  1,000. 

In  Blood  of  the  Ox  (Marcet) 1-62 

"  Lymph  (Nasse). 0'56 

"  Cephalo-rachidian  Fluid  (Lassaigne) 0*60 

"  Compact  Tissue  of  Tibia  in  Male  of  38  years  (Valentin)  2 '00 
"  Spongy  Tissue  of  the  same  (Valentin) 0-70 

Function  of  Carbonate  of  Soda. — This  substance  has  a 
tendency  to  maintain  the  fluidity  of  the  fibrin  and  albumen  of 
the  blood,  and  assists  in  preserving  the  form  and  consistence 
of  the  blood  corpuscles.  Its  function  with  regard  to  nutri- 
tion is  rather  accessory,  like  that  of  chloride  of  sodium,  than 
essential,  like  the  phosphate  of  lime  in  the  constitution  of 
certain  structures. 


MAGNESIA,   ETC.  45 

Origin  and  Discharge  of  Carbonate  of  Soda. — This  sub- 
stance is  not  introduced  into  the  body  as  carbonate  of  soda, 
but  is  formed,  as  is  the  carbonate  of  lime  in  part,  by  a  de- 
composition of  the  malates,  tartrates,  etc.,  which  exist  in 
fruits.  It  is  discharged  occasionally  in  the  urine  of  the  hu- 
man subject,  and  a  great  part  of  it  is  decomposed  in  the 
lungs  by  the  action  of  pneumic  acid,  setting  free  carbonic 
acid,  which  is  discharged  in  the  expired  air. 

Carbonate  of  Potassa,  KO,  C02. 

This  salt  exists  particularly  in  herbivorous  animals.  It 
is  found  in  the  human  subject  when  subjected  to  a  vegetable 
diet.  Under  the  heads  of  function,  origin,  and  discharge, 
what  has  been  said  with  regard  to  the  carbonate  of  soda  will 
apply  to  the  carbonate  of  potash. 

Carbonate  of  Magnesia,  MgO,  C02HO,  and  Bicarbonate  of 
Soda,  NaO,  CO3  +  HO,  C(V 

It  is  most  convenient  to  take  up  these  two  salts  in  con- 
nection with  the  other  carbonates,  though  they  are  put  at  the 
end  of  the  list  of  inorganic  substances,  as  the  least  important. 
We  know  very  little  about  them,  chemically  or  physiologi- 
cally. Traces  of  carbonate  of  magnesia  have  been  found 
in  the  blood  of  man,  and  it  exists  normally  in  considerable 
quantity  in  the  urine  of  herbivora.  In  the  human  subject 
it  is  discharged  in  the  sebaceous  matter. 

Liebig  has  merely  indicated  the  presence  of  bicarbonate 
of  soda  in  the  blood. 

Phosphate  of  Magnesia,  3  MgO,  PO5  +  7  HO ;  Phosphate 
of  Soda  (neutral),  3  NaO,  PO5 ;  and  Phosphate  of  Potassa, 
2  KO,  P06. 

1  Formula  of  Graham,  op.  cit.,  p.  389. 


46  INTRODUCTION. 

These  salts  are  found  in  all  the  fluids  and  solids  of  the 
body,  though  not  existing  in  a  very  large  proportion,  com- 
pared with  the  phosphate  of  lime,  which  we  have  already 
considered.  In  their  relations  to  organized  structures,  they 
are  analogous  to  the  phosphate  of  lime ;  entering  into  the 
composition  of  the  tissues,  and  existing  there  in  a  state  of 
intimate  combination.  They  are  all  taken  into  the  body 
with  food,  especially  by  the  carnivora,  in  the  fluids  of  which 
they  are  found  in  much  greater  abundance  than  the  carbo- 
nates ;  which  latter,  as  we  have  already  seen,  are  in  great 
part  the  result  of  the  decomposition  by  carbonic  acid  of  the 
malates,  tartrates,"  oxalates,  etc. 

With  respect  to  their  functions,  we  can  only  say  that, 
with  the  phosphate  of  lime,  they  go  to  form,  and  are  neces- 
sary constituents  of,  the  organized  structures. 

They  are  discharged  from  the  body  in  the  urine  and 
feces. 

Sulphate  of  Soda,  ISTaO,  SO  3  +  10  HO ;  Sulphate  of 
Potassa,  KO,  SO3 ;  Sulphate  of  Lime,  CaO,  SO3  +  2  HO. 

The  sulphate  of  soda  and  the  sulphate  of  potassa  a,re 
identical  in  their  situation,  and  apparently  in  their  functions. 
They  are  found  in  all  the  fluids  and  solids  of  the  body,  ex- 
cepting milk,  bile,  and  gastric  juice.  Their  origin  in  the 
body  is  from  the  food,  in  which  they  are  contained  in  small 
quantity,  and  they  are  discharged  in  the  urine.  Their  chief 
function  appears  to  be  in  the  blood,  where  they  tend  to  pre- 
serve the  fluidity  of  the  fibrin  and  albumen,  and  the  form 
and  consistence  of  the  blood  corpuscles. 

The  sulphate  of  lime  is  found  in  the  blood  and  feces.  It 
is  introduced  into  the  body  in  solution  in  the  water  which  is 
used  as  drink,  and  is  discharged  in  the  feces. 

Its  function  is  not  understood,  and  is  probably  not  very 
important. 


SUMMARY   OF  INOKGANIC   PRINCIPLES.  47 

Hydrochlorate  of  Ammonia,  2sH3,  HC1. 

This  substance  has  simply  been  indicated  by  chemists  as 
existing  in  the  gastric  juice  of  ruminants,  the  saliva,  tears, 
and  urine.  Some  chemists  make  a  rearrangement  of  its  par- 
ticles, calling  it  chloride  of  ammonium,  when  instead  of 
]N"H3,  HC1,  it  would  be  NH4C1;  but  as  the  ammonium  is 
hypothetical,  the  name  we  have  used  seems  more  appropriate. 

It  is  discharged  in  the  urine,  in  which  it  exists,  according 
to  Simon,1  in  the  proportion  of  0*41  parts  per  1,000.  Its 
origin  and  function  are  unknown. 

Summary. — A  review  of  the  functions  of  the  individual 
inorganic  constituents  of  the  body,  excluding  the  gases,  will 
show  that  they  may  be  divided  into  two  groups :  one,  which 
is  composed  of  those  substances,  existing  particularly  in  the 
solids  and  semi-solids,  which  are  in  a  condition  of  molecular 
union  with  organic  substances,  merge  their  identity,  as  it 
were,  into  them,  and  become  necessary  constituents  of  the 
tissues  /  and  the  other,  composed  of  substances  which  rather 
regulate,  by  their  influence  in  endosmosis,  or  otherwise,  the 
nutritive  processes^  do  not  seem  to  be  indispensable  constituents 
of  the  tissues,  lut  have  rather  an  accessory  office  to  perform 
in  the  function  of  nutrition. 

At  the  head  of  the  first  group  we  may  place  water  ;  the 
absence  of  which  involves  destruction  of  the  properties  of 
the  tissues,  and  even  of  the  organic  elements. 

At  the  head  of  the  second  group  we  may  place  common 
salt ;  which  is  absolutely  necessary  to  the  functions  of  nutri- 
tion, though  it  does  not  seem  to  form  an  indispensable  ele- 
ment of  the  tissues. 

The  first  group,  as  we  should  naturally  expect,  forms  a 
considerable  proportion  of  the  body,  and  the  articles  compo- 
sing it  are  discharged  in  small  quantity ;  as  in  the  case  of 

1  SIMON,  Animal  Chemistry,  with  Reference  to  the  Physiology  and  Pathology 
of  Man,  Philadelphia,  1846,  p.  403. 


4:8  INTRODUCTION. 

water,  which  composes  two-thirds  of  the  entire  organism,  and 
yet  only  about  four  and  a  half  pounds  are  discharged  daily 
from  the  skin  and  lungs,  and  in  the  urine  and  feces. 

The  second  group  enters  and  is  discharged  from  the  body 
in  considerable  quantity,  and  very  little  remains  in  the  or- 
ganism; as  common  salt,  which  exists  in  the  urine  in  a 
greater  proportion  than  in  any  of  the  solids  or  other  fluids. 

The  following  are  the  inorganic  substances  which  are  ap- 
parently indispensable  to  the  constitution  of  organized  tissues : 

Water. 

Basic  Phosphate  of  Lime. 
Carbonate  of  Lime. 
Phosphate  of  Magnesia. 

"          u  Soda, 
"          "  Potassa. 

The  following  are  those  which  appear  to  have  an  accessory 
office  in  nutrition : 

Chloride  of  Sodium. 

"        "  Potassium. 
Carbonate  of  Soda. 
Bicarbonate  of  Soda. 
Carbonate  of  Potassa. 

"        "  Magnesia. 
Sulphate  of  Soda. 

«         "   Potassa. 

The  remaining  two  principles,  sulphate  of  lime  and  hy- 
drochlorate  of  ammonia,  are  so  obscure  in  their  function  that 
they  cannot  be  definitely  put  in  either  of  the  above  groups. 

ORGANIC   NON-NITROGENIZED   PRINCIPLES. 

(Hydro-  Carbons.} 

The  principles  of  this  class  differ  widely  from  inorganic 
substances  In  the  first  place,  they  have  a  different  origin, 


STJGAKS.  49 

being  formed  exclusively  in  animal  or  vegetable  bodies.  They 
are  of  definite  chemical  composition,  and  crystallizable.  The 
most  important  groups  of  this  class,  i.  e.  the  sugars  and  fats,  are 
composed  of  carbon,  hydrogen,  and  oxygen,  whence  they  are 
sometimes  called  Hydro-Carbons.  They  are  distinguished 
from  another  class  of  organic  substances  by  the  fact  that 
they  do  not  contain  nitrogen ;  which  has  given  them  the 
name  of  Non-nitrogenized  Principles.  They  are  in  part 
introduced  into  the  body  as  food,  and  in  part  formed  in  the 
economy  by  special  organs.  In  the  former  instance,  they 
undergo  an  elaborate  preparation  by  digestion  before  they 
become  part  of  the  organism,  differing  in  this  respect  from 
the  inorganic  principles,  which  are  absorbed  unchanged 
With  the  exception  of  butter  and  the  sugar  of  milk,  they  are 
never  discharged  from  the  body  in  health,  but  disappear  in 
the  processes  of  nutrition.  In  this  respect,  also,  they  differ 
from  the  inorganic  principles,  all  of  which  are  discharged 
from  the  body,  most  of  them  in  the  condition  in  which  they 
entered. 

The  most  important  principles  of  this  class  may  be  divided 
into  two  great  groups,  the  Sugars  and  the  Fats  ;  in  addition 
to  which  we  have,  lactic  acid  and  the  lactates,  pneumic  acid, 
pneumate  of  soda,  the  fatty  acids  and  their  combinations, 
and  certain  organic  salts  which  are  found  in  the  bile. 


The  varieties  of  sugar  with  which  we  are  most  familiar, 
of  which  cane  sugar  may  be  taken  as  the  type,  are  not 
found  in  the  animal  body,  but  belong  to  the  vegetable 
kingdom.  These,  which  form  an  important  element  of 
food,  must .  be  modified  by  digestion  before  they  become 
proximate  principles.  For  a  long  time  it  was  supposed 
that  sugar  was  an  exclusively  vegetable  production  and 
consumed  by  animals ;  but  late  experiments,  especially  those 
of  Bernard,  have  shown  that  sugar  is  constantly  produced  by 
animals,  presenting,  in  this  instance,  marked  differences  from 
4 


50  INTRODUCTION. 

the  vegetable  varieties.  Yegetable  sugar  taken  as  food  is 
changed  so  as  to  resemble  animal  sugar,  before  it  is  absorbed. 
In  considering,  then,  the  proximate  principles  of  the  body,  we 
have  only  to  do  with  the  animal  sugars. 

There  are  two  varieties  of  sugar  manufactured  in  the 
economy.  The  first  is  constantly  formed  by  the  liver,  and  is 
found  in  this  organ  and  the  blood  which  circulates  between 
it  and  the  lungs.  This  variety  is  called  Liver  Sugar  /  and,  as 
it  appears  in  the  urine  of  diabetics,  is  sometimes  known  un- 
der the  name  of  diabetic  sugar.  The  second  variety  is  only 
present  in  the  organism  during  lactation.  It  exists  in  the 
milk,  and  is  called  Milk  Sugar.  We  have  also  sugar  resulting 
from  the  transformation  by  digestion  of  cane  sugar  and  starch, 
which  is  called  Glucose.  This  resembles  the  liver  sugar  very 
closely,  and  is,  indeed,  identical  with  it  in  composition,  but 
differs  from  it  in  the  fact  that  it  ferments  less  easily. 

The  presence  of  sugar  in  the  economy  seems  to  be  a  ne- 
cessity of  existence.  It,  or  starch  which  is  readily  converted 
into  glucose,  constitutes  an  important  and  necessary  element 
of  food.  In  early  life  large  quantities  are  taken  in  with  the 
milk.  This,  however,  does  not  seem  to  be  sufficient  to  supply 
the  wants  of  the  system,  and  we  have  it  continually  manufac- 
tured in  the  interior  of  the  body  ;  but  once  formed,  or  intro- 
duced from  without,  it  undergoes  some  transformation  innutri- 
tion, and  is  never  discharged  in  health.  Sugar  is  exceedingly 
soluble,  and  in  the  economy,  exists  in  solution  in  the  blood. 
Here  it  forms  a  union  with  the  chloride  of  sodium,  which 
masks,  to  a  certain  extent,  some  of  its  characteristic  proper- 
ties, such  as  the  peculiar  taste  by  which  it  is  so  readily 
.recognized. 

Composition  and  Properties. — The  sugars  are  composed 
of  carbon,  hydrogen,  and  oxygen ;  and  it  is  noticeable  that  the 
hydrogen  and  oxygen  always  exist  in  equal  proportions,  or 
in  the  proportions  which  form  water ;  a  peculiarity  affording 
an  explanation  of  the  transformation  of  one  variety  of  sugar 


SUGAES.  51 

into  another,  which  is  effected  in  some  instances  with  great 
facility. 

Simon  1  gives  the  following  composition  of  the  animal 
sugars  in  a  crystalline  form  : 

Liver  Sugar  and  Glucose,  CI2H14OU. 
Milk  Sugar,  C12H12O12. 

On  exposing  either  of  these  varieties  of  sugar  to  a  dry 
heat,  two  atoms  of  water  of  crystallization  are  driven  off, 
leaving  the  formula  for  liver  sugar,  C12H12O12,  and  for  milk 
sugar,  C12H10O10.  From  the  relative  composition  of  these 
varieties  of  sugar,  it  is  seen  that  the  addition  of  two  atoms 
of  hydrogen  and  oxygen,  or  water,  to  milk  sugar,  will  trans- 
form it  into  glucose.  This  change  actually  takes  place  in 
digestion.  The  digestive  fluids  act  also  upon  cane  sugar 
(C12HuOn)  and  starch  (C12H]0O10),  transforming  them  into 
glucose. 

Animal  sugars  are  distinguished  from  cane  sugar  by 
their  different  behavior  in  the  presence  of  acids  and  alkalis. 
Cane  sugar  is  converted  into  the  animal  variety  by  boiling 
for  a  few  seconds  with  a  dilute  mineral  acid,  and  is  unaffected 
by  boiling  with  an  alkali;  while  the  animal  sugars  are  not 
affected  by  acids,  and  are  transformed  into  a  dark-brown 
substance,  melassic  acid,  by  boiling  with  an  alkali. 

If  .a  solution  of  sugar  be  mixed  with  a  little  fresh  yeast 
and  kept  for  a  few  hours  at  a  temperature  of  from  80°  to 
100°  Fahr.,  a  peculiar  change  takes  place  which  is  called  fer- 
mentation. The  sugar  is  decomposed  into  carbonic  acid  gas, 
which  rises  to  the  top  in  bubbles,  and  alcohol,  which  remains 
in  the  liquid.  Some  ferments,  especially  organic  matters  in 
process  of  decomposition,  when  they  exist  in  a  saccharine 
solution,  have  the  property  of  inducing  a  change  of  the  sugar 
into  lactic  acid  (C6H0O6),  giving  rise  to  what  is  called  the 
lactic-acid  fermentation.  This  process  is  peculiarly  interest- 

1  SIMON'S  Chemistry  of  Man,  Philadelphia,  1846. 


52  INTRODUCTION. 

ing  in  a  physiological  point  of  view,  from  the  fact  that  much 
of  the  sugar  which  disappears  in  the  economy  is  now  thought 
to  undergo  this  change. 

A  clear  solution  of  sugar  has  a  peculiar  effect  upon  polar- 
ized light,  being  possessed  of  what  is  called  a  rotatory  power. 
If  a  ray  of  polarized  light  be  gassed  through  a  tube  contain- 
ing simple  water,  its  direction  is  unchanged ;  but  if  a  saccha- 
rine solution  be  substituted,  it  is  found  to  possess  what  is 
called  molecular  activity,  and  turns  the  ray  to  the  right.  The 
amount  of  deviation,  which  can  easily  be  measured  by  an 
instrument  constructed  for  this  purpose  by  Biot  and  Soleil, 
called  a  polarimeter,  indicates  the  quantity  of  sugar  in  the  solu- 
tion. The  instrument  above  mentioned  is  sometimes  used 
for  quantitative  analysis. 

Tests  for  Sugar. — Eeliable  tests  for  determining  the 
presence  of  sugar  in  the  animal  tissues  and  fluids  are  useful 
to  the  practical  physician  as  well  as  the  physiologist;  for 
this  substance  frequently  occurs  in  the  urine,  as  a  pathological 
condition,  when  it  is  essential  to  ascertain  the  fact  of  its 
presence,  even  if  no  attempt  be  made  to  determine  its  quan- 
tity. For  this  purpose  a  number  of  tests  have  been  devised, 
which  are  most  of  them  reliable  and  simple  of  application. 

Moords,  or  the  Potash  Test. — This  test  depends  on  the 
conversion  of  the  animal  sugars  into  melassic  acid  by  boiling 
with  a  caustic  alkali.  It  is  employed  in  the  following  way : 
To  a  small  portion  of  the  suspected  liquid  in  a  test  tube  we 
add  a  little  caustic  potash  in  solution,  and  boil  the  mixture. 
If  sugar  be  present,  a  brownish  color  will  be  produced,  its 
intensity  depending  upon  the  quantity  of  sugar.  This  test 
is  applicable  only  to  glucose,  grape  sugar,  and  the  animal 
varieties. 

Trommels  Test. — This  is  one  of  the  most  delicate  and 
convenient  tests  for  sugar.  It  is  employed  in  the  following 


SUGARS.  53 

way :  To  the  suspected  liquid  in  a  test  tube,  we  add  one  or 
two  drops  of  a  moderately  strong  solution  of  sulphate  of 
copper,  and  render  the  mixture  distinctly  alkaline  by  the 
addition  of  caustic  potash  in  solution.  On  the  addition  of 
the  alkali  the  mixture  will  assume  a  distinctly  blue  color, 
especially  marked  if  sugar  be  present.  On  the  application 
of  heat,  if  sugar  be -present,  a  little  before  the  liquid  reaches 
the  boiling  point,  a  yellowish  or  reddish  precipitate  will 
begin  to  show  itself  in  the  upper  part  of  the  test  tube,  which 
as  the  heat  continues  will  gradually  extend  through  the  whole 
of  the  liquid.  If  no  sugar  be  present,  the  liquid  will  retain 
its  clear  blue  color,  unless  the  boiling  be  prolonged,  when  a 
black  precipitate  of  the  black  oxide  of  copper  is  likely  to 
appear.  In  this  test,  before  the  heat  is  applied,  the  copper 
is  in  the  form  of  the  sulphate  of  a  protoxide  (CuO,  SO3), 
which  is  soluble;  but  on  boiling  in  an  alkaline  solution, 
the  sugar  becomes  oxidized,  is  transformed  into  an  acid, 
the  nature  of  which  is  not  well  determined,  and  the  copper, 
losing  an  equivalent  of  oxygen,  becomes  reduced  to  the  con- 
dition of  a  sub-oxide  (Cu2O),  which  has  a  reddish  or  yellow- 
ish color,  and  is  insoluble.  This  is  the  way  in  which  the  test 
is  generally  employed.  Trommer  recommended  (1841),  with 
special  reference  to  examination  of  urine,  to  first  add  the 
solution  of  potash,  then  filter,  and  then  add  the  solution  of 
copper.  If  sugar  be  present,  a  reduction  of  the  sub-oxide  will 
take  place  spontaneously  in  a  few  hours,  or  may  be  produced 
immediately  by  boiling.  This  removes  certain  sources  of 
obscurity  in  examining  the  urine,  which  result  from  a  pre- 
cipitate produced  by  the  simple  action  of  the  potash,  and  not 
dependent  on  the  presence  of  sugar. 

If  care  be  taken  to  employ  the  following  simple  precau- 
tions in  the  application  of  this  test,  it  will  be  found  the  most 
reliable  and  simple  of  any  that  are  in  use  for  qualitative 
analysis. 

The  solution  to  be  examined  must  be  clear.  A  clear 
extract  of  the  blood,  muscles,  or  liver,  is  easily  made  in  the 


54:  INTRODUCTION. 

following  way  :  The  blood,  or  tissue,  finely  divided,  is  boiled 
with  a  little  water  and  sulphate  of  soda.  In  a  few  moments 
the  organic  and  coloring  matters  will  become  coagulated, 
when  it  is  to  be  thrown  on  a  filter,  and  a  clear  extract  will 
pass  through.  This  extract  will  contain  sulphate  of  soda, 
which  is  very  soluble  in  hot  watgr,  but  this  does  not  interfere 
with  the  application  of  the  test.  The  same  result  may  be 
obtained  by  boiling  with  animal  charcoal,  enough  being 
added  to  make  a  thin  paste,  and  filtering ;  a  process,  how- 
ever, which  is  more  tedious  and  has  no  advantages  over  the 
one  just  described. 

In  testing  the  urine,  a  light  flocculent  precipitate  will 
generally  be  obtained,  though  no  sugar  be  present.  "With 
a  little  experience  this  may  be  distinguished  from  the 
deposit  of  sub-oxide  of  copper,  by  the  fact  that  it  is  less 
highly  colored,  and  appears  in  flakes  after  it  finally  settles 
to  the  bottom  of  the  test  tube,  of  a  light  grayish  color ; 
while  the  sub-oxide  of  copper  settles  to  the  bottom  in  the 
form  of  a  heavy  red  powder.  If  there  be  any  doubt  as  to 
the  nature  of  the  reaction,  the  urine  may  be  purified  in  va- 
rious ways  before  testing.  A  very  simple,  and  perhaps  the 
best  method,  is  to  make  a  paste  with  animal  charcoal  and 
filter.  Robin  recommends  the  following  process:  "To  be 
certain  of  the  presence  of  glucose,  we  free  it  (the  liquid)  from 
all  reducing  matters ;  1st,  adding  to  the  urine  an  excess  of 
the  neutral  acetate  of  lead,  then  filtering ;  2d,  adding  to  this 
clear  filtered  liquid,  ammonia,  until  it  is  slightly  alkaline, 
and  filtering.  We  can  then  treat  the  second  liquid  with  the 
reagents ;  and  if  it  precipitates,  it  is  certain  that  there  is  sugar 
in  the  urine." :  Another  method  is  to  evaporate  the  urine  to 
the  consistence  of  a  syrup,  extract  this  with  alcohol,  drive 
off  the  alcohol  by  evaporation,  and  dissolve  the  residue  in 
water;  when  if  sugar  be  present  it  will  respond  to  the  test. 


1  Didionnaire  de  Medecine,  etc.,  de  P.  H.  NYSTEN,  par  E.  LITTRE  et  CH.  ROBIN, 
Paris,  1858.     "  Sucre." 


SUGAES.  55 

It  is  a  curious  fact  that  sugar  added  to  healthy  urine,  even 
in  large  quantity,  will  not  respond  to  Trommer's  test,  on 
account  of  organic  matters,  which  interfere  with  the  reduc- 
tion of  the  copper.  The  cause  of  this  interference  we  do  not 
understand ;  but  in  diabetes,  the  organic  substances,  whatever 
they  may  be,  are  not  present,  or  at  least  do  not  interfere  with 
the  application  of  tests  for  sugar. 

Another  precaution  to  be  adopted  is  to  add  a  small  quan- 
tity, two  or  three  drops  only,  of  the  solution  of  sulphate  of 
copper,  especially  if  we  suspect  the  sugar  to  be  present  in 
small  quantity ;  for  if  too  much  be  added,  a  portion  only  of 
the  oxide  of  copper  will  be  reduced,  and  that  which  remains, 
by  its  blue  color,  may  obscure  the  reaction. 

Ban^eswiWs  Test. — For  those  engaged  in  physiological 
investigations,  when  it  is  desired  to  roughly  estimate  the 
quantity  of  sugar  in  any  clear  extract,  and  when  the  test  is 
to  be  employed  very -frequently,  Barreswill's  solution  is  con- 
venient. This  is  simply  a  solution  of  tartrate  of  copper  and 
caustic  potash.  The  reaction  with  this  fluid  is  precisely  the 
same  as  in  Trommer's  test.  It  has  seemed  to  me,  if  there  be 
any  difference,  that  the  reduction  takes  place  more  promptly 
with  the  sulphate  of  copper,  but  that  the  tartrate  will  detect 
a  smaller  quantity  of  sugar.  The  advantage  of  Barreswill's 
test  is,  that  but  a  single  fluid  is  to  be  added  to  the  suspected 
solution.  The  only  disadvantage  is,  that  the  solution  is  liable 
to  alteration  if  kept  more  than  a  few  days  or  weeks.  After 
standing  for  a  certain  time,  a  yellowish  sediment  is  deposited, 
and  the  fluid  will  no  longer  reduce  in  the  presence  of  sugar. 
Its  properties  may  be  renewed  by  adding  a  little  potash  and 
iiltering ;  but  in  delicate  observations,  it  is  always  better  to 
use  a  solution  which  has  not  undergone  alteration. 

In  employing  this  test,  we  add  to  the  suspected  fluid 
enough  of  the  solution  to  give  the  whole  a  distinctly  blue 
color,  and  boil ;  if  sugar  be  present,  we  have  a  reduction  of 
the  yellowish  sub-oxide  of  copper  as  in  Trommer's  test. 


56  INTRODUCTION. 

The  solution  may  be  prepared  according  to  the  following 
formula,  reduced  to  grains  from  the  formula  given  by' Ber- 
nard : 1 

Of  bitartrate  of  potash,  3  vi.  gr.  xxiij. 

Of  crystallized  carbonate  of  soda,  3  v.  gr.  ix. 

Dissolve  in  §  vss.  of  water  ^  add  to  the  solution  3  iij.  gr. 
li.  of  sulphate  of  copper,  and  boil ;  allow  the  mixture  to 
cool  and  add  3  v.  gr.  ix.  of  potash  dissolved  in  5  iv.  of  water. 
Add  water  till  the  whole  measures  3  xvii. 

Maumen&s  Test. — B'6ttger*s  Test. — The  first  of  these 
tests  is  employed  by  saturating  strips  of  some  woollen  tissue, 
such  as  flannel,  with  a  strong  solution  of  bichloride  of  tin, 
and  drying.  One  of  these  strips  is  moistened  with  the  sus- 
pected liquid,  and  dried  quickly  by  the  heat  of  a  fire  or  lamp. 
If  sugar  be  present,  the  strips  will  assume  a  brownish  or  black 
tint. 

Bottger's  test  depends  upon  the  reduction  of  a  salt  of  bis- 
muth, analogous  to  the.  reduction  of  the  copper  in  Trommer's 
test.  It  is  employed  in  the  following  way :  We  add  to  the 
suspected  liquid  a  few  drops  of  a  weak  solution  of  the  nitrate 
of  bismuth  in  nitric  acid,  render  the  whole  alkaline  by  the 
addition  of  a  solution  of  carbonate  of  soda,  and  boil  for  three 
or  four  minutes.  If  sugar  be  present,  the  bismuth  will  be 
reduced,  and  form  a  dark  precipitate.  Neither  of  these  tests 
presents  any  advantage  over  Trommer's  test,  which  is  the  one 
most  generally  employed. 

Fermentation  Test. — With  the  exception  of  actual  ex- 
traction, this  is  the  most  certain  test  for  sugar,  and  should 
always  be  employed  when  the  other  tests  leave  any  doubt 
with  regard  to  its  presence.  It  depends  on  a  property  of 
sugar  whereby  it  is  decomposed  into  alcohol  and  carbonic 
acid  in  the  presence  of  certain  ferments,  at  a  moderately  ele- 
vated temperature.  The  test  is  applicable  to  all  varieties  of 

1  BERNARD,  Lemons  de  Physiologic  Expirimcntalc,  Paris,  1855,  p.  34. 


6UGAKS.  67 

sugar;  but  it  must  be  remembered  that  milk  sugar  fer- 
ments slowly  and  with  difficulty.  In  its  application,  all  that 
is  necessary  is  to  add  a  few  drops  of  fresh  yeast,  and  keep 
the  suspected  liquid  for  a  few  hours  at  a  temperature  of  from 
80°  to  100°  Fahr.  The  mixture  should  be  placed  in  some  appa- 
ratus by  which  the  gas  which  forms  may  be  collected  and  an- 
alyzed. To  effect  this,  we  may  fill  a  large  test  tube  and  in  vert  it 
in  a  small  shallow  vessel ;  or  if  there  be  but  a  small  quantity  of 
liquid,  we  may  use  a  very  simple  and  convenient  apparatus 
described  by  Bernard.  This  is  simply  a  large  test  tube  fitted 
with  a  good  cork,  perforated  to  allow  the  passage  of  a  small 
tube  which  extends  to  the  bottom.  This  tube  may  be  turned 
up  at  the  lower  end,  and  bent  above  so  as  to  permit  the 
escape  of  the  liquid  as  the  gas  is  formed.  The  whole  is  com- 
pletely filled  with  the  suspected  solution,  to  which  have  been 
added  a  few  drops  of  fresh  yeast,  and  kept  at  a  temperature 
of  80°  to  100°  Fahr.  If  sugar  be  present,  bubbles  of  gas  will 
soon  begin  to  appear,  which  will  collect  at  the  top  and  force 
a  portion  of  the  liquid  out  by  the  small  tube.  If  no  gas  has 
appeared  at  the  end  of  four  or  six  hours,  it  is  certain  that  no 
sugar  is  present.  This  test  is  conclusive,  if  proper  care  be 
taken  in  its  application  ;  and  to  insure  accuracy,  it  is  well  to 
test  the  yeast  with  a  saccharine  solution  to  demonstrate  its 
activity,  and  test  it  also  with  pure  water,  to  be  sure  that  it 
contains  no  sugar.  "We  may  then  demonstrate  that  the  gas 
produced  is  carbonic  acid  by  removing  the  cork  and  inserting 
a  lighted  taper,  which  will  be  immediately  extinguished,  or 
passing  it  into  another  vessel  and  agitating  with  lime-water, 
which  will  be  rendered  milky  by  the  formation  of  the  insolu- 
ble carbonate  of  lime.  The  alcohol  remains  in  the  liquid, 
from  which  it  may  be  separated  by  careful  distillation. 

Measures  for  demonstrating  the  composition  of  the  gas 
and  the  presence  of  alcohol  in  the  liquid  are  by  no  means 
necessary  in  the  ordinary  application  of  the  test.  The  dis- 
tinct formation  of  gas  in  the  liquid  is  generally  sufficient 
evidence  of  the  presence  of  sugar. 


58  INTRODUCTION. 

Torulce. — Another  test  of  the  presence  of  sugar  is  the 
growth  of  the  Torulce  cerevisice.  After  diabetic  urine  has 
stood  for  some  time  at  a  moderate  temperature,  a  delicate 
scum  will  form  upon  the  surface,  which,  on  microscopic 
examination,  will  be  found  to  consist  of  a  vegetable  growth, 
presenting  a  number  of  oval  joints  irregularly  connected. 
These  are  called  Torulce.  After  a  time  they  break  up  and 
fall  to  the  bottom  of  the  vessel,  as  minute  oval  spores.  This 
appearance  is  observed  even  when  a  small  quantity  of  sugar 
is  present. 

Yarious  modes  of  procedure  have  been  described  for  the 
determination  of  the  quantities  of  sugar.  In  general  terms 
it  may  be  stated  that  the  copiousness  of  the  precipitate  in 
Trommer's  test,  and  the  amount  of  gas  evolved  in  the  fer- 
mentation test,  give  some  idea  of  the  quantity  of  sugar 
present.  For  directions  for  accurate  quantitative  analysis  the 
reader  is  referred  to  works  on  organic  chemistry. 

Origin  and  Functions  of  Sugar. — Sugar  is  an  important 
element  of  food  at  all  periods  of  life.  In  the  young  child  it 
is  introduced ,  in  considerable  quantity  with  the  milk."  In 
the  adult  it  is  introduced  partly  in  the  form  of  cane  sugar, 
but  mostly  in  the  form  of  starch,  which  is  converted  into 
sugar  in  the  process  of  digestion.  With  the  exception  of 
milk  sugar,  which  is  present  only  during  lactation,  all  the 
sugar  in  the  body  exists  in  a  form  resembling  glucose,  into 
which  milk  sugar,  cane  sugar,  and  starch  are  all  converted, 
either  before  they  are  absorbed,  or  as  they  pass  through  the 
liver.  In  addition  to  these  external  sources  of  sugar,  it  is 
continually  manufactured  in  the  economy  by  the  liver, 
whence  it  is  taken  up  by  the  blood  passing  through  this 
organ.  It  disappears  from  the  blood  in  its  passage  through 
the  lungs.  Sugar  is  found  then  in  the  economy  con- 
stantly, in  the  substance  of  the  liver,  in  the  blood  coming 
from  the  liver,  and  in  the  blood  of  the  right  side  of  the 
heart;  and  after  the  ingestion  of  saccharine  or  amylaceous 


STJGAKS.  59 

articles  of  food,  in  the  blood  of  the  portal  vein.  It  is  not 
found  in  other  organs,  nor  does  it  normally  exist  in  the 
arterial  blood. 

During  the  first  three  or  four  months  of  foetal  life  sugar 
is  formed  by  the  placenta,  and  exists  in  all  the  fluids  of  the 
foetus,  in  greater  quantity  even  than  after  birth.  At  the 
third  or  fourth  month  the  liver  begins  to  take  on  this  func- 
tion, which  is  gradually  lost  by  the  placenta.  The  constant 
production  of  this  principle  in  the  economy,  even  in  the 
early  months  of  foetal  life,  is  significant  of  the  importance  of 
its  function. 

The  function  of  sugar  and  its  mode  of  disappearance  in 
the  economy  are  not  yet  well  understood.  Its  early  forma- 
tion in  large  quantity,  when  the  processes  of  nutrition  are 
most  active,  seems  to  point  to  an  important  office  in  the 
performance  of  this  general  function.  Its  presence  is  un- 
doubtedly necessary  at  all  periods  of  life ;  for  its  formation 
never  ceases  in  health.  Bernard  has  attempted  to  show  that 
its  presence  in  the  animal  fluids  favors  cell  development,  but 
has  hardly  succeeded  in  establishing  this  fully.1 

It  has  been  claimed  that  the  sugars  and  fats  are  for  the 
purpose  of  keeping  up  the  animal  temperature,  and  are 
oxidized  or  undergo  combustion  in  the  lungs.  This  view 
was  afterwards  modified  by  Liebig  and  others,  who  supposed 
that  the  oxidation  takes  place  in  the  general  system.  This 
theory  will  be  discussed  more  fully  in  the  chapter  on  animal 
heat.  Here  we  can  only  say  that,  while  there  are  many  cir- 
cumstances which,  taken  by  themselves,  might  lead  to  such 
a  conclusion,  the  production  of  heat  in  the  body  is  closely 
connected  with  the  general  process  of  nutrition,  of  which  the 
disappearance  of  oxygen  and  formation  of  carbonic  acid  are 
but  a  single  one  of  many  important  changes.  "We  have  not  yet 
sufficient  ground  for  the  supposition  that  the  substances  under 
consideration  are  directly  and  exclusively  acted  upon  by  oxy- 

1  BERNARD,  Lemons  de  Physiologic  Uxperimcntale,  Paris,  1855,  p.  247  et  seq. 


60  INTRODUCTION. 

gen  in  the  organism.  The  term  calorific  elements,  which 
is  sometimes  applied  to  them,  cannot  therefore  be  accepted. 
When  we  endeavor  to  substitute  for  this  theory  a  definite  ex- 
planation of  the  uses  of  sugar  in  the  economy,  we  find  our- 
selves at  a  loss ;  but  it  must  be  remembered  that  we  are  yet  far 
from  having  a  complete  knowledge  of  the  functions  of  the 
body,  particularly  those  connected  with  the  intimate  pro- 
cesses of  nutrition. 

In  the  present  state  of  science,  we  are  only  justified  in 
saying  that  sugar  is  important  in  the  process  of  development 
and  nutrition,  at  all  periods  of  life.  The  precise  way  in 
which  it  influences  these  processes  is  not  fully  understood. 

Sugar  disappears  from  the  blood  in  its  passage  through 
the  lungs,  in  great  part,  probably,  by  conversion  into  lactic 
acid.  This  change  has  been  demonstrated  in  the  blood  of  a 
diabetic  patient ;  all  the  sugar  contained  in  the  blood  being 
thus  changed  in  less  than  twenty  minutes.1 

Sugar  is  never  discharged  from  the  body  in  health,  with 
the  single  exception  of  the  sugar  of  milk  in  the  female  during 
lactation.  Under  certain  diseased  conditions  of  the  system 
its  production  by  the  liver  is  exaggerated,  so  that  a  certain 
quantity  passes  through  the  lungs,  exists  in  the  arterial  blood, 
and  appears  in  the  urine,  constituting  the  very  serious  affec- 
tion, called  diabetes  mellitus. 

Fats. 

Fatty  or  oily  matters  exist  in  both  the  animal  and 
vegetable  kingdoms.  Those  which  are  most  interesting  to 
us  as  physiologists  are  the  varieties  found  in  animals,  which 
constitute  an  important  group  of  proximate  principles.  Both 
vegetable  and  animal  fats  are  important  elements  of  food. 

In  the  animal  economy  fat  exists  in  three  varieties,  which 
are  called,  respectively,  Oleine,  Margarine,  and  Stearins. 
In  certain  situations  are  found  some  of  the  fatty  acids  and 

1  ROBIN  and  YERDEIL,  Chimie  Anatomique,  tome  ii.,  p.  553. 


FATS.  61 

their  combinations,  but  they  exist  in  minute  quantity,  and 
their  function  is  comparatively  unimportant. 

Composition  and  Properties. — In  their  ultimate  composi- 
tion, fats  bear  a  certain  resemblance  to  the  sugars.  Like 
them  they  are  composed  of  carbon,  hydrogen,  and  oxygen ; 
but  the  two  latter  elements  do  not  exist,  as  in  sugar,  in  the 
proportions  to  form  water.  From  this  difference  we  should 
be  led  to  suspect,  what  is  really  the  fact,  that  the  different 
varieties  of  fat  are  not  mutually  convertible. 

The  fat  which  exists  in  the  body  is  a  mixture  of  the  three 
varieties  above  mentioned,  and  is  found  in  the  ordinary  adi- 
pose tissue,  and  in  the  substance  of  certain  tissues  in  the 
form  of  minute  globules  or  granules.  It  is  not  found  in  any 
great  quantity  in  the  blood,  except  after  digestion  of  a  full 
meal.  It  exists  in  the  chyle  in  a  state  of  extremely  minute 
subdivision  and  suspension.  It  exists  in  the  milk,  also  in  a 
state  of  minute  subdivision,  but  presenting  some  slight  differ- 
ences from  the  ordinary  fatty  matter  of  the  economy. 

Robin  and  Yerdeil  give,  as  the  ultimate  composition  of 
Stearine,  C71H70O8.  The  other  varieties  are  separated  from 
their  union  with  each  other  with  great  difficulty,  and  have 
not  yet  been  obtained  in  a  state  of  sufficient  purity  for  ulti- 
mate analysis.  The  reaction  of  all  the  varieties  of  fat  is 
neutral. 

Fat,  in  greater  or  less  quantity,  is  found  in  all  the  tissues 
of  the  body,  with  the  exception  of  the  substance  of  the  bones, 
the  teeth,  and  the  elastic  and  inelastic  fibrous  tissue.  It 
always  consists  of  a  mixture  of  the  three  varieties  in  varying 
proportions,  but,  with  one  or  two  exceptions,  is  never  com- 
bined with  any  other  of  the  proximate  principles.  In  the 
adipose  tissue  proper,  it  is  enclosed  in  little  cells  which  are 
called  the  adipose  vesicles.  In  all  other  situations  it  is  in  the 
form  of  microscopic  globules  or  granules.  As  it  is  thus  dis- 
tinct from  other  elements,  it  may  be  always  recognized  in  the 
organism  by  the  naked  eye  or  the  microscope.  In  the  ner- 


62  INTRODUCTION. 

vous  matter  there  exists  a  phosphorized  fat,  the  composition 
and  properties  of  which  are  not  very  well  understood,  in 
union  with  organic  matter.  A  minute  quantity  of  fat  exists 
in  combination  with  the  organic  matter  of  the  blood  corpus- 
cles. 

The  fats  are  insoluble  in  waier  and  in  the  animal  fluids, 
with  the  exception  perhaps  of  the  bile,  which  holds  a  small 
quantity  in  solution  by  virtue  of  its  saponaceous  constituents. 
They  are  all  very  soluble  in  ether  and  hot  alcohol,  and  but 
slightly  soluble  in  cold  alcohol.  The  varieties  which  are  solid 
at  the  temperature  of  the  body,  stearin e  and  margarine,  are 
easily  dissolved  by  oleine,  which  is  liquid. 

The  most  marked  distinction  between  the  varieties  of  fat 
is  in  their  consistence.  Oleine  is  liquid  at  the  temperature 
of  the  body,  and  even  at  the  freezing  point  of  water.  Mar- 
garine is  liquid  at  or  above  the  temperature  of  118°,  and 
stearine  at  the  temperature  of  143°  Fahr.  The  difference  in 
the  consistence  of  adipose  tissue  of  different  animals  depends 
upon  the  relative  proportion  of  the  various  kinds  of  fat. 

Saponification. — When  fat  is  boiled  for  a  certain  time 
with  an  alkali,  in  the  presence  of  water,  it  undergoes  a  pecu- 
liar decomposition  which  is  called  saponification.  A  portion 
of  the  water  is  appropriated,  and  the  fat  is  converted  into 
glycerine  and  an  acid.  The  acid  is  called  oleic,  margaric, 
or  stearic  acid,  as  it  is  formed  from  oleine,  margarine,  or 
stearine.  In  this  process  the  glycerine  remains  uncombined, 
and  the  acid  unites  with  the  alkali  to  form  what  is  commonly 
known  as  a  soap. 

This  kind  of  decomposition  is  called  saponin'cation  by  a 
base ;  but  technically,  saponification  is  regarded  as  any  pro- 
cess by  which  a  fat  is  decomposed  into  its  acid  and  glycerine. 
This  may  be  effected  by  passing  the  vapor  of  water  through 
fat  which  has  been  raised  to  a  temperature  of  572°  Fahr.  The 
action  of  the  strong  acids  is  also  to  decompose  fat.  "When  a 
small  quantity  of  acid  is  used,  it  unites  with  the  glycerine ; 


FATS.  63 

I 

when  a  large  quantity  is  used,  it  unites  with  the  fatty  acid. 
The  process  of  formation  of  glycerine  and  fatty  acids  in- 
volves the  fixation  of  a  certain  quantity  of  water ;  so  that 
the  combined  weights  of  the  glycerine  and  acid  exceed  that 
of  the  fat  originally  employed.1  It  is  thought  by  some  that 
this  acidification  of  fat  takes  place  to  a  certain  extent  in  di- 
gestion ;  however  this  may  be,  it  is  not  an  essential  part  of 
the  digestive  process. 

Emulsion. — When  liquid  fat  is  violently  shaken  up  with 
water,  it  is  minutely  subdivided,  and  an  opaque  milky  mix- 
ture is  the  result.  But  this  is  momentary,'  the  two  liquids 
separating  almost  immediately  from  each  other  when  they 
are  no  longer  agitated.  There  are  certain  fluids,  however, 
which  have  the  property  of  holding  fat  permanently  in  a 
state  of  minute  subdivision  and  suspension,  forming  what  is 
called  an  emulsion.  Out  of  the  body,  mucilaginous  fluids 
and  white  of  egg  have  this  property.  In  the  body,  we  find 
as  examples  of  emulsions  the  chyle,  which  is  formed  by  the 
action  of  the  pancreatic  juice  upon  the  fatty  elements  of 
food,  and  milk,  which  is  composed  of  butter  held  in  suspen- 
sion by  the  water  and  caseine.  The  property  of  forming 
emulsions  with  certain  liquids  is  one  of  the  most  interesting 
attributes  of  the  fats,  as  it  is  in  this  form  only  that  it  can 
find  its  way  from  the  alimentary  canal  into  the  general 
system. 

Origin  and  Functions  of  Fat. — One  source  of  fat  in  the 
economy  is  the  food.  It  constitutes  an  important  article  of 
diet,  existing  in  animal  food  in  the  form  of  adipose  tissue, 
and  mingled  to  a  certain  extent  with  the  muscular  tissue. 
Yegetable  oil  also  is  quite  a  common  article  of  food.  When 
introduced  in  the  form  of  adipose  tissue,  the  fat  is  freed  from 
its  vesicles  by  the  action  of  the  gastric  juice,  is  generally 

1  REGNAULT,  Cours  filementaire  de  Chimie,  Paris,  1853,  tome  iv.,  p.  414. 


O£  INTRODUCTION. 

melted  at  the  temperature  of  the  body,  and  floats  in  the  form 
of  oil  on  the  alimentary  mass.  It  passes  then  into  the  smal] 
intestines  unchanged,  is  emulsified  by  the  pancreatic  juice, 
and  absorbed  by  the  lacteals.  A  small  quantity  of  fat  is 
absorbed  by  the  radicles  of  the  portal  vein.  After  a  full 
meal,  the  blood  of  a  carnivorous  animal  frequently  contains 
enough  fatty  emulsion  to  form  a  thick  white  pelicle  on  cooling. 

The  question  as  to  the  possibility  of  the  formation  of  fat 
in  the  organism  may  be  now  considered  as  definitely  settled. 
It  has  been  shown  by  Liebig,  Boussingault,  and  others,  that 
in  young  animals  especially,  the  fat  in  the  body  cannot  all  be 
accounted  for  by  that  which  has  been  taken  in  as  food  added 
to  that  which  the  body  contained  at  birth.  The  experiments 
of  Boussingault,1  on  this  point,  on  young  pigs,  are  very  con- 
clusive, and  demonstrate  that  fat  must  be  produced  some- 
where in  the  organism.  Bernard 2  has  shown  that  an  emul- 
sive substance,  which  he  regards  as  fat  in  combination  with 
organic  nitrogenized  matters,  is  produced  by  the  liver,  and 
is  taken  up  by  the  blood  of  the  hepatic  vein.  He  believes 
that  it  is  produced  at  the  expense  of  the  amylaceous  or  sac- 
charine elements  of  food. 

It  is  very  certain  that  the  generation  or  deposition  of 
fat  •  in  the  body  may  be  influenced  very  considerably  by 
diet,  and  the  conditions  of  the  system.  This  is  daily  exem- 
plified in  the  inferior  animals,  and  is  true,  though  it  is  not 
perhaps  as  universal,  in  the  human  subject.  It  has  been 
found  that  a  diet  consisting  largely  of  fatty,  amylaceous,  and 
saccharine  principles  favors  the  accumulation  of  fat,  while 
an  exclusively  nitrogenized  diet  is  unfavorable  to  it,  and  will 
produce  emaciation,  if  rigidly  followed.  Muscular  activity, 
it  is  well  known,  is  unfavorable  to  the  accumulation  of  fat ; 
which  may  account  in  a  measure  for  its  greater  relative  quan- 
tity in  the  female.  In  some  individuals,  especially  when  its  ac- 

1  BOUSSINGAULT,  Chimie  Agricole,  Paris,  1854. 

8  BERNARD,  Lemons  de  Physiologic  Experimentale,  Paris,  1855,  p.  154  et  seq. 


FATS.  65 

cumulation  is  excessive,  there  is  an  hereditary  tendency  to  fat. 
Organs  which  are  in  process  of  atrophy  from  disease,  or  other 
causes,  are  apt  to  be  the  seat  of  a  deposit  of  fatty  granules ; 
as  the  muscular  fibres,  which,  in  many  diseases  character- 
ized by  rapid  emaciation,  are  found  to  be  the  seat  of  fatty 
degeneration. 

There  are  certain  situations  where  fat  never  exists,  as  in 
the  eyelids  and  scrotum ;  and  others  where  it  is  always  found, 
even  in  extreme  emaciation,  as  in  the  orbit  and  around  the 
kidneys.  Ordinarily,  fat  is  pretty  well  distributed  through- 
out the  body,  having  a  tendency  to  accumulate,  however, 
beneath  the  skin,  and  in  the  omentum,  where  its  presence  is 
least  likely  to  interfere  wTith  the  function  of  parts,  and  where 
it  serves  to  maintain  the  uniform  temperature  of  the  body, 
and  particularly  of  the  delicate  abdominal  organs. 

The  average  relative  quantity  of  fat  in  the  human  body 
has  been  calculated  by  Burdach  to  be  five  parts  per  hundred. 
In  the  body  of  a  man  weighing  176  pounds,  he  found  8'8 
pounds  of  fat.1 

In  certain  parts  fat  has  an  important  mechanical  func- 
tion. It  serves  as  a  soft  bed  for  delicate  organs,  as  the  eye 
and  kidney.  It  is  a  bad  conductor,  and  thus  prevents  the 
loss  of  heat  by  the  organism.  This  is  very  important  in 
some  warm-blooded  animals,  as  the  whale,  in  which  the  loss 
of  heat  would  be  very  great  were  it  not  for  the  immensely 
thick  layer  of  fat  just  beneath  the  skin.  It  is  important  in 
filling  up  the  interstices  between  the  muscles,  bones,  ves,- 
sels,  &c. 

Fat,  like  sugar,  has  undoubtedly  an  important  office  in 
connection  with  the  general  processes  of  development  and  nit- 
trition.  We  have  not  yet  arrived  at  an  accurate  knowledge 
of  the  changes  which  it  undergoes  as  it  is  used  up  by  the 
economy ;  for  with  the  single  exception  of  butter  in  the  milk, 


1  BURDACH,  Traite  de  Physiologic,  Paris,  1837,  tome  viii.,  p.  80.     Translated-' 
from  the  German  by  Jourdan. 


bO  INTRODUCTION. 

it  is  never  discharged  from  the  body  in  health.  We  have 
already  alluded  to  the  view  that  the  sugars  and  fats  are 
respiratory  or  calorific  elements,  which  undergo  oxidation 
in  respiration,  and  are  immediately  concerned  in  the  produc- 
tion of  animal  heat.  One  of  the  arguments  in  favor  of  this 
function  of  fat  has  been  that  ip.  cold  climates,  where  there  is 
a  greater  demand  for  the  generation  of  heat  by  the  system, 
fat  is  a  more  common  and  more  abundant  article  of  diet. 
This  is  undoubtedly  true,  but  other  principles  are  consumed 
in  greater  quantity,  and  the  general  process  of  nutrition,  of 
which  the  production  of  heat  is  but  a  single  phenomenon,  is 
intensified.  There  is  not  sufficient  ground  for  supposing  that 
fat  has  any  such  exclusive  function.  Its  office  is  connected 
with  the  general  process  of  nutrition ;  and  its  various  trans- 
formations in  connection  with  this  function,  we  have  as  yet 
been  unable  to  follow. 

Fatty  Acids  and  Soaps. — In  addition  to  the  fatty  sub- 
stances just  described,  the  following  fatty  acids,  free,  and 
united  with  bases  to  form  soaps,  have  been  found  in  the  blood : 

Oleic  Add  (C36H33O3HO), 
Margaric  Acid  (C34H33O3HO) 
Oleate  of  Soda, 
Mar  gar  ate  of  Soda. 

Oleic  and  margaric  acids  have  been  detected  in  minute 
quantities  in  a  free  state  in  the  blood  and  bile.  Their 
function  is  unknown.  The  oleate  and  margarate  of  soda  are 
found  in  small  quantity  in  the  blood,  bile,  and  lymph.  They 
serve  to  hold  in  solution  the  small  quantity  of  the  fatty  acids 
and  fats  which  exists  in  these  fluids.  The  function  of  all 
these  substances  is  comparatively  unimportant.  In  the  blood 
of  the  ox,  Robin  and  Yerdeil  have  found  a  small  quantity  of 
;Stearic  acid  and  the  stearate  of  soda. 

Odorous  Principles. — It  is  well  known  that  the  perspira- 


,  ODOROT76   PRINCIPLES.  67 

tion  of  certain  parts,  as  the  axilla  and  sometimes  the  feet,  has 
a  distinct  odor.  This  is  supposed  to  be  due  to  combinations 
of  volatile  fatty  acids  with  soda  and  potassa.  Most  of  the 
inferior  animals  have  a  distinctive  odor,  which  may  generally 
be  readily  recognized,  and  is  always  strongly  developed  in 
the  blood  by  the  addition  of  sulphuric  acid.  Barreul  gives 
the  following  conclusions  as  the  result  of  an  extended  series 
of  observations  on  this  subject : 

"1.  That  the  blood  of  every  species  of  animal  contains 
a  principle  peculiar  to  each  one.  2.  This  principle,  which 
is  very  volatile,  has  an  odor  like  that  of  the  perspiration. 

3.  The  volatile  principle  is  in  a  state  of  combination  in  the 
blood,  and  while  this  combination  exists  it  is  not  appreciable. 

4.  When  this  combination  is  destroyed,  the  principle  of  the 
blood  becomes  volatile,  and  from  that  time  it  is  not  only 
possible,  but  very  easy  to  recognize  the '  animal  to  which  it 
belongs.     5.  In  each  species  of  animal  the  odorous  principle 
is  manifested  with  greater  intensity  in  the  male  than  in  the 
female.     6.  The  combination  of  this  odorous  principle  is  in 
a  state  of  solution  in  the  blood  which  permits  it  to  be  devel- 
oped either  in  the  blood  entire,  in  the  defibrinated  blood,  or 
in  the  serum.     7.  Of  all  the  means  employed  for  setting  free 
the  odorous  principle  of  the  blood,  concentrated  sulphuric 
acid  is  that  which  succeeds  the  best.    It  suffices  to  add  one- 
third  or  one-half  of  the  volume  of  blood  employed,  and  a  few 
drops  of  blood  is  sufficient."  1 

Lactic  Acid — Pneumic  Acid — Pneumate  of  Soda. 

Lactic  acid  may  be  formed  by  what  is  called  the  lactic  acid 
fermentation  of  sugars,  particularly  sugar  of  milk.  This  kind 
of  action  is  induced  by  the  presence  of  certain  organic  fer- 
ments, or  by  organic  nitrogenized  matter  in  process  of  de- 
composition. This  principle  does  not  exist,  as  was  at  one 

1  ROBIN  and  VEKDIEL,  op.  cit.,  tome  iiL,  p.  90. 


68  INTRODUCTION. 

time  supposed,  in  fresh  milk,  but  only  after  it  has  become 
sour.  Its  composition  (CGH5O5  +  HO)  assimilates  it  to  the 
sugars,  and  indicates  how  it  may  be  formed  theoretically  from 
them  by  transposition  of  their  atoms  ;  milk  sugar  having  for 
its  composition  012H12O12,  which  is  also  the  formula  for  an- 
hydrous glucose. 

It  is  a  constant  constituent  of  the  gastric  juice,  and  is 
indispensable  to  the  digestive  properties  of  this  secretion. 

Lactic  acid  has  been  demonstrated  by  Liebig  in  the 
juice  of  muscular  tissue.1 

Sources  and  Function. — This  principle  may  be  formed,  in 
minute  quantity,  in  the  intestines,  from  the  saccharine  and 
amylaceous  articles  of  food ;  but  it  is  in  greatest  part  pro- 
duced in  the  economy  as  an  element  of  secretion.  It  is 
thought  that  a  great  portion  of  the  sugar  which  passes  in  the 
blood  from  the  liver  to  the  lungs  is  converted  into  lactic  acid. 
If  this  be  the  case,  it  unites  with  bases  and  is  almost  imme- 
diately decomposed  and  lost.  Lactates  in  the  blood  are  very 
readily  converted  into  carbonates,  as  has  been  shown  by  the 
experiments  of  Lehmann,2  who  took  into  the  stomach  half  an 
ounce  of  dry  lactate  of  soda,  and '  in  thirteen  minutes  his 
urine  had  an  alkaline  reaction  from  the  presence  of  carbon- 
ates. Alkalinity  of  the  urine  from  this  cause  is  often  pro- 
duced by  the  ingestion  of  combinations  of  the  vegetable  acids 
in  fruits,  etc. 

The  most  marked  function  of  lactic  acid  is  in  the  gastric 
juice,  and  will  be  considered  under  the  head  of  digestion. 

Pneumic  Acid  and  Pneumate  of  Soda. — Pneumic  acid 
was  discovered  and  extracted  from  the  tissue  of  the  lungs  by 
Yerdeil  in  1851. 3  Its  ultimate  composition  is  not  given. 
According  to  this  author,  it  exists  in  the  lungs  of  the  mam- 

1  LEHMANN,  Physiological  Chemistry,  Philadelphia,  1855,  voL  i.,  p.  90. 

2  Ibid,  p.  97. 

8  ROBIN  and  VERDEIL,  op.  cit.,  tome  il,  p.  466. 


ORGANIC   PRINCIPLES.  C9 

malia  at  all  periods  of  life.  He  extracted  about  three-fourths 
of  a  grain  from  the  perfectly  healthy  lungs  of  a  female  who 
was  guillotined.  It  has  not  been  found  in  other  situations. 

Its  function  is  connected  with  respiration.  The  carbon- 
ates and  bicarbonates  of  the  blood,  in  passing  through  the 
lungs,  are  in  part  decomposed  by  pneumic  acid,  a  certain 
portion  of  the  carbonic  acid  in  the  expired  air  being  evolved 
in  this  way. 

Pneumate  of  Soda  is  produced  by  the  action  of  pneumic 
acid  upon  the  carbonates  of  soda  in  the  blood,  and  is  found 
in  the  blood  which  passes  through  the  lungs.  It  is  not  dis- 
charged from  the  body,  undergoing  in  the  system  some 
transformation  with  which  we  are  unacquainted*. 

ORGANIC   NITROGENIZED   PRINCIPLES. 

Principles  of  this  class  differ  essentially  from  all  the  other 
constituents  of  the  body.  They  are  the  only  elements  en- 
dowed with  what  are  called  vital  properties,  and  upon  them 
depend  all  the  phenomena  which  characterize  living  struc- 
tures. This  important  fact  cannot  be  too  fully  insisted  upon. 

All  the  vital  phenomena  which  take  place  in  the  lody 
depend  primarily  upon  organic  nitrogenized  principles,  which 
are  the  only  elements  in  the  organism  endowed  with  life. 

By  a  tissue  or  fluid  endowed  with  life  is  meant : 

A  combination  of  proximate  principles  which  has  the  prop- 
erty, under  certain  conditions,  of  appropriating  materials  for 
its  nourishment  and  regenerating  itself  ,  to  repair  the  continual 
destruction  or  waste  to  which  all  living  ~bodies  are  subject. 

This,  which  is  the  great  process  of  NUTRITION,  is  going 
on  from  the  beginning  to  the  end  of  life ;  its  phenomena 
are  distinct  from  those  which  take  place  in  inert  com- 
pounds, and  are  called  vital.  Take,  for  example,  the  nutri- 
tive processes  which  take  place  in  the  muscles  or  the  bones. 
In  common  with  all  pails  of  the  body,  these  tissues  arc 
continually  undergoing  waste.  The  circumstances  under 


TO  INTRODUCTION. 

which  they  can  supply  this  waste,  or  regenerate  themselves  by 
the  appropriation  of  suitable  materials,  involve  contact  with 
the  circulating  blood.  They  take  materials  from  this  fluid  and 
change  them  into  their  own  substance.  This  process  takes 
place  only  in  living  bodies,  and  is  unknown  in  the  inorganic 
kingdom.  As  it  is  the  great  cliaracteristic  of  life,  its  accom- 
plishment being  the  end  and  object  of  all  the  functions  of 
the  organism,  the  study  of  these  organic  principles  is  mani- 
festly of  the  greatest  importance.  We  shall  find  that  their 
properties  are  peculiar  to  themselves,  and  their  chemical  study 
must  necessarily  be  eminently  physiological.  To  arrive  at 
any  definite  idea  of  their  properties,  the  methods  of  study 
which  have  been  generally  employed  by  chemists  must  be 
discarded,  as  by  these  they  are  reduced  to  inorganic  ele- 
ments, and  treated  simply  as  combinations  of  inert  sub- 
stances. They  must  be  studied  as  nearly  as  possible  in  the 
condition  in  which  they  exist  in  the  body ;  which  is  neces- 
sarily the  condition  in  which  they  are  capable  of  manifesting 
their  characteristic  vital  phenomena. 

These  principles  are  found  in  all  the  fluids,  semi-solids, 
and  solids  of  the  body,  except  the  excrementitious  fluids.1 
The  nutritive  fluids  contain  several.  In  each  tissue  an  or- 
ganic principle  is  found  which  presents  certain  peculiarities 
more  or  less  distinctive.  They  are  all  formed  in  the  or- 
ganism, and,  with  the  exception  of  the  milk,  a  little  mucus, 
desquamated  epidermis  and  epithelium,  and  an  almost  inap- 
preciable quantity  exhaled  by  the  lungs  and  skin,  are  never 
discharged  unchanged  from  the  body,  in  health.  They 
assunie  the  consistence  of  the  part  in  which  they  are  found ; 
being,  therefore,  fluid,  semi-solid,  and  solid.  They  constitute 
by  far  the  greater  part  of  the  organism ;  but  their  quantity 
in  the  whole  body  has  never  been  accurately  estimated. 
Their  reaction  is  neutral.  As  a  peculiarity  of  chemical  com- 
position, they  all  contain  nitrogen ;  whence  they  are  called 

1  The  excrementitious  fluids  contain  coloring  matters,  which  Robin  and  Verdeil 
put  in  this  class,  but  which  do  not  seem  to  be  endowed  with  vital  properties. 


OEGAJSTIC   PRINCIPLES.  71 

Nitrogenized  Principles.  They  all  closely  resemble  one  of 
the  most  important  and  certainly  the  most  carefully  studied 
of  their  number,  namely,  albumen ;  whence  they  are  some- 
times called  Albuminoids.  They  were  regarded  by  Mulder 
as  compounds  of  a  theoretical  radical  or  base  which  he 
called  Proteine,  and  after  this  chemist  are  sometimes  called 
Proteine  com/pounds. 

Composition  and  Properties. — 1.  Studied,  as  they  gener- 
ally have  been,  from  a  purely  chemical  point  of  view,  they 
are  regarded  by  many  as  solid  substances  in  solution  in  the 
fluids,  in  a  condition  approximating  to  this  in  the  semi-solids, 
and  of  course  as  solid  in  the  solids,  like  the  bones  and  teeth. 
This  view  is  erroneous,  as  we  shall  see  that  some  are  natu- 
rally fluid,  some  are  semi-solid,  and  some  are  solid.  In  this 
condition  they  have  been  found  to  consist  of  Carbon,  Hydro- 
gen, Oxygen,  Nitrogen,  with  sometimes  a  little  Sulphur  and 
Phosphorus.  The  coloring  matters  contain  in  addition  a 
small  proportion  of  Iron.  By  ultimate  analysis  they  have  been 
found  to  be  of  indefinite  chemical  composition*  which,  indeed, 
we  would  be  led  to  expect  from  the  state  of  continual  change 
in  which  they  exist  in  the  body.  By  the  method  em- 
ployed in  arriving  at  their  ultimate  composition,  even  before 
analysis,  they  are  completely  destroyed  as  organic  principles 
by  desiccation,  and  rendered  incapable  of  exhibiting  any  of 
their  characteristic  properties.  The  composition  of  their 
dry  residue  only  is  thus  given,  while  in  reality  they  all  con- 
tain more  or  less  water,  which  enters  into  their  composition, 
and  deprived  of  which  they  cannot  be  called  organic  sub- 
stances. The  proportion  of  water  is  to  some  extent  variable, 
but  confined  within  tolerably  narrow  limits.2 

2.  The  organic  principles  never  exist  alone,  but  always  in 

1  ROBIN  and  VERDEIL,  op.  cit.,  tome  iii.,  p.  147. 

2  For  a  further  discussion  of  this  important  subject,  see  an  article  by  the  author 
in  the  American  Journal  of  the  Medical  Sciences,  October,  1863,  On  the  Organic 
Nitrogenized  Principles  of  the  Body,  ivith  a  New  Method  for  their  Estimation  in 
tfie  Blood. 


INTRODUCTION. 

combination  with  inorganic  substances,  which,  though  per- 
haps not  absolutely  necessary  to  the  properties  by  which  they 
are  recognized  out  of  the  body,  are  essential  in  the  perform- 
ance of  their  vital  functions  in  the  economy.  Under  these  cir- 
cumstances the  organic  and  inorganic  principles  are  so  closely 
united,  that  the  latter  may  be.  said  to  acquire,  by  virtue  of 
this  union,  vital  properties.  Though  unaltered,  the  inorganic 
are  discharged  with  the  worn-out  organic  substances,  and, 
combined  with  fresh  organic  matter,  are  deposited  in  the 
tissues  in  the  process  of  regeneration. 

3.  The  organic  principles  which  are  naturally  fluid  may 
be  coagulated,  but  under  no  circumstances  do  they  assume  a 
definite  or  crystalline  form.    We  should  be  led  to  expect  this 
from  the  fact  that  they  have  no  absolutely  fixed  composition. 
When  the  liquids  of  this  class  are  thus  solidified,  they  are 
not  precipitated  from  a  solution,  but  are  made  to  assume 
a  new  form,   still  retaining    their  water   of   composition. 
When  exposed  to  evaporation,  whether  they  be  fluid  or  semi- 
solid,  their  water  may  be  driven  off,  and  they  are  said  to  be 
desiccated.     They  can  be  made  to  assume  their  water  of 
composition  again  by  simple  contact,  as  they  have  in  a  high 
degree  the  property  of  Tiygrometmcity .     Both  these  properties 
are  peculiar  to  organic  substances. 

4.  When  exposed  to  a  very  elevated  temperature,  that 
which  has  been  considered  by  chemists  as  the  organic  sub- 
stance .  proper  is  volatilized  and  driven  off,  leaving  the  inor- 
ganic substances,  which  always  enter  into  its  composition. 

5.  In  their  natural  condition,  the  organic  principles  have 
no  very  distinct  odor ;  but  when  exposed  for  some  time  to  a 
moderate  heat,  certain  odorous  or  empyreumatic  substances 
are  produced.     This  change  is  peculiar  to  organic  matters, 
and  takes  place  in  the  process  of  cooking.     When  these  ele- 
ments are  used  as  food,  this  process  serves  a  useful  purpose, 
rendering  them  more  agreeable  to  the  taste,  and  facilitating 
their  digestion. 

6.  One  of  the  great  distinctive  properties  of  organic  prin- 


ORGANIC  PRINCIPLES.  73 

ciples,  out  of  the  body,  is  putrefaction.  In  contact  with 
the  air,  at  a  moderate  temperature,  they  undergo  decompo- 
sition into  carbonic,  lactic,  and  butyric  acids,  and  ammonia. 
When  this  change  has  once  commenced,  it  has  been  found 
by  "Wurtz  to  continue  in  a  vacuum.1  Putrefaction  is  a 
process  peculiar  to  organic  substances.  By  it  they  are 
transformed  into  substances  which  are  used  in  the  nutrition 
of  vegetables  ;  and  as  vegetables  are  eventually  consumed  by 
animals,  the  animal  matter  is  not  lost,  but  returns  again 
through  this  channel,  so  that  the  two  kingdoms  are  continu- 
ally interchanging  elements.  Organic  matters  in  putrefac- 
tion are  capable  of  setting  up  the  same  process  in  other 
articles  of  this  class  by  simple  contact,  neither  giving  up  nor 
taking  away  any  chemical  elements.  They  are  then  called 
ferments,  and  this  action  is  said  to  be  catalytic.  As  before 
remarked,  this  constitutes  one  of  the  most  important  charac- 
teristics of  organic  matters ;  one,  indeed,  which  enables  us 
to  recognize  them  when  they  exist  in  quantities  too  minute  for 
chemical  analysis,  as  in  exhalations  from  the  pulmonary  and 
cutaneous  surfaces. 

Proteine. — In  1838,  just  after  the  promulgation  of  the 
theory  of  vegetable  organic  radicals  by  Liebig  and  Dumas, 
Mulder  attempted  to  show  that  the  organic  animal  substan- 
ces were  all  compounds  of  a  radical  which  he  called  Prote- 
ine. This  theory  was  pretty  generally  received,  and  gave  to 
organic  matters  the  name  of  Proteine  Compounds,  by  which 
they  are  sometimes  known.  He  treated  albumen,  fibrin,  and 
ca seine  with  alcohol  and  ether  to  remove  the  fats,  and  with 
hydrochloric  acid  to  remove  inorganic  salts  ;  dissolved  them, 
thus  purified,  in  a  solution  of  potash,  and  precipitated  with 
acetic  acid  a  substance  said  to  possess  always  the  same  char- 
acters, which  he  called  proteine ;  and  which,  by  union  with  a 
certain  quantity  of  sulphur  and  phosphorus,  was  capable 
of  forming  fibrin,  albumen,  and  caseine.  But  the  analyses 

1  Cited  by  ROBIN  and  VERDEIL,  op,  cit.:  tome  Hi.,  p.  142. 


74  INTRODUCTION. 

of  different  chemists  have  shown  that  proteine  itself  has  an 
indefinite  chemical  composition,  hardly  any  two  formulae 
being  the  same.  It  is  essentially  an  artificial  product ;  and 
with  the  views  we  have  taken  of  the  composition  of  organic 
substances,  there  is  not  the  slightest  reason  to  suppose  that 
it  plays  the  part  of  a  base  or  radical  for  a  group  of  definite 
compounds.  It  is  not  a  distinct  chemical  substance,  for 
its  composition  is  indefinite ;  nor  a  proximate  principle,  for  it 
is  produced  artificially  and  by  decomposition.  We  must 
therefore  reject  the  theory  that  it  serves  as  the  radical  of  a 
definite  series,  and  discard  the  name  of  Proteine  Compounds, 
as  applied  to  organic  principles. 

Catalysis. — Catalysis,  or  catalytic  action,  is  a  name  given 
to  a  certain  process  which  we  do  not  as  yet  understand.  The 
word  was  introduced  by  Berzelius  in  1835,  and  applied  to 
certain  actions  or  affinities  brought  into  play  in  inorganic 
bodies  by  the  mere  presence  of  another  substance,  the  latter 
not  undergoing  any  chemical  alteration.  It  is  now  applied 
to  all  chemical  changes  which  are  induced  by  the  simple 
presence  of  any  substance,  like  the  particular  class  of  sub- 
stances called  ferments,  in  which  the  substance  inducing  this 
action  undergoes  no  chemical  change.  Fermentation,  which 
was  considered  in  treating  of  sugar,  is  an  example  of  catalysis ; 
the  sugar  being  decomposed  into  carbonic  acid  and  alcohol  from 
the  fact  of  the  mere  presence  of  yeast,  which  has  nothing  to 
do,  chemically,  with  the  process.  Putrefaction,  which  we 
have  just  considered,  is  an  example  of  catalysis ;  for  a  small 
quantity  of  any  animal  substance  in  a  state  of  putrefaction 
is  capable,  ~by  its  presence,  of  setting  up  the  same  process  in 
other  principles  of  this  class.  Nutrition,  and  to  a  certain  ex- 
tent digestion,  are  examples  of  catalysis ;  for  in  the  repair 
of  the  system,  certain  materials  are  taken  from  the  blood  by 
the  tissues,  and  by  the  latter  changed  into  different  sub- 
stances,  as  musculine  for  the  muscles,  osteine  for  the  bones, 
etc. ;  and  in  digestion,  the  organic  elements  which  are  dissolved 


ORGANIC   PRINCIPLES.  75 

are  changed  by  the  presence  of  certain  organic  substances  in 
the  digestive  fluids.  Any  process  set  up  by  the  mere  presence 
of  substances,  which  themselves  undergo  no  chemical  change, 
or  the  transformation  of  one  variety  of  organic  matter  into 
another  from  the  mere  fact  of  contact,  is  called  catalysis. 

The  general  properties  we  have  mentioned  are  possessed 
by  all  organic  principles ;  which,  indeed,  differ  from  each  other 
very  little  in  their  general  characters,  and  even  in  ultimate 
composition.  Those  which  go  to  form  the  tissues  are  endowed 
with  identical  vital  properties.  Robin  and  Yerdeil  give  seven- 
teen distinct  substances  belonging  to  this  class,  of  which  four 
are  coloring  matters.1  But  three  of  these  principles  have  been 
carefully  studied  with  reference  to  their  ultimate  composition ; 
but  their  composition,  which  is  indefinite,  and  not  necessary 
to  their  vital  properties,  is  of  little  physiological  interest. 
The  number  of  equivalents  of  the  various  ultimate  elements 
is  entirely  arbitrary,  as  these  principles  enter  into  no  definite 
combinations. 

Table  of  Organic  Principles. 

Name.  Where  Found. 

'Fibrin  (CM8HM60MX4oSa) ,  .Blood,  Chyle,  Lymph. 

(  Blood,  Chyle,  Lymph, 
Albumen  «WW>.N.A) j  Serosuics,  ant. 

Albuminose Chyme,  Blood. 

Caseine  (C288H2280PON36S2) Milk. 

Mucosine Mucus. 

Pancreatine Pancreatic  Juice. 

^Pepsin Gastric  Juice. 

Globuline Blood  Globules. 

Musculine Muscles. 

Osteine Bone. 


o 


Cartilagine Cartilage. 

Elasticine Elastic  Jissue. 

Keratine Nails,  Hair,  Epidermis. 

.  Crystalline Crystalline  Lens. 


1  These  authors  do  not  consider  that  pepsin  has  been  fully  established  as  a 
distinct  proximate  principle.  Its  distinctive  properties  seem  to  be  sufficiently 
well  marked,  and  it  has  therefore  been  included  in  the  list. 


76  INTKODUCTION. 

Name.  Where  Found. 


60 


.      HEematine  ......  "  f  Coloring  Matter  of  Blood. 


***»  .......     AU  contain  Iron 

•3   os     Bihverdme  ......  Bile. 

°        [Urrosacine  ......  J  ^      "  "       Urine. 

fibrin. 

Fibrin  is  found  in  the  Wood,  lymph,  and  chyle.  In 
the  first-named  fluid  it  exists  in  considerable  quantity,  but 
in  the  last  two  it  is  much  less  abundant.  Its  quantity  has 
been  estimated  by  chemists  in  all  the  above-mentioned  fluids, 
but  the  analyses  which  are  generally  given  represent  dried 
fibrin,  and  give  us  no  definite  idea  of  its  quantity  in  the  form 
in  which  it  naturally  exists.  The  quantity  of  fibrin  in  the 
blood,  estimated  by  the  author  by  a  process  in  which  it  is 
not  exposed  to  desiccation,  is  between  8  and  9  parts  per 
1000.1  This  proportion  is  undoubtedly  quite  variable  within 
the  limits  of  health.  According  to  Becquerel  and  Eodier,2  its 
quantity  is  considerably  increased  during  gestation,  and  is 
greater  in  adults  than  in  very  young  or  very  old  persons. 
As  a  general  rule,  it  is  more  abundant  in  arterial  than  in 
venous  blood,  and  is  often  entirely  absent  from  the  blood  of  the 
hepatic  and  renal  veins.  No  constant  difference  in  quantity 
has  been  established  in  the  sexes,  and  its  proportion  appears 
to  bear  no  definite  relation  to  the  vigor  of  the  individual. 

It  appears  in  the  blood  at  about  the  fifteenth  day  of  intra- 
uterine  life,  and  exists  constantly  from  that  time. 

The  composition  of  fibrin  is  given  in  the  table.  It  con- 
tains carbon,  hydrogen,  oxygen,  nitrogen,  and  a  little  sulphur. 
The  proportion  of  these  substances,  however,  is  indefinite, 
and  the  formula,  like  that  of  all  the  principles  of  this  class, 
is  entirely  arbitrary,  as  it  enters  into  no  definite  combina- 
tions, and  consequently  has  no  combining  equivalent.  Its 
ultimate  composition  is  comparatively  unimportant,  for  it 

1  See  article  in  Am.  Jour.,  loc.  cit.     Though  the  ordinary  methods  of  analysis 
do  not  give  the  real  quantities  of  fibrin,  they  give  important  results  with  regard  to 
the  comparative  quantities  in  different  situations. 

2  BECQUEREL  and  RODIEK,  Traite  de  Chimie  Pathologique,  p.  101  et  scq. 


ORGANIC   PRINCIPLES.  77 

gives  us  no  indication  of  the  properties  by  which  it  is  recog- 
nized, nor  of  its  functions ;  and,  indeed,  has  been  found  to 
differ  little,  if  at  all,  from  the  composition  of  masculine  or 
albumen,  the  properties  of  which  are  very  different. 

Fibrin  may  be  easily  extracted  from  the  fluids  in  which 
it  exists.  Perhaps  the  best  mode  of  procedure  is  to  whip 
the  fluid,  freshly  drawn,  with  a  bundle  of  twigs  or  broom 
corn.  In  this  way  the  fibrin  may  be  quickly  and  completely 
separated.  It  is  then  freed  from  foreign  matters,  such  as 
blood-corpuscles,  by  washing  under  a  stream  of  water,  at  the 
same  time  kneading  with  the  fingers. 

Fibrin  is  not,  as  is  supposed  by  many,  a  solid  substance 
in  solution  in  the  liquids  in  which  it  is  found.  It  is  naturally 
liquid  and  mingled  with  the  watery  elements.  After  coagu- 
lation it  contains  a  certain  proportion  of  water,  capable,  it  is 
true,  of  being  driven  off  by  evaporation,  but  nevertheless 
water  of  composition,  deprived  of  which  it  loses  the  prop- 
erties by  which  we  recognize  it  as  fibrin. 

Properties  of  Fibrin. — The  striking  peculiarity  by  which 
fibrin  is  recognized  is  its  spontaneous  coagulability.  All  the 
fluids  in  which  it  is  contained,  when  drawn  from  the  body  or 
placed  under  abnormal  conditions,  become  more  or  less 
coagulated,  and  their  coagulating  principle  is  called  fibrin. 
It  is  this  substance,  therefore,  which  gives  to  the  blood  its 
peculiar  and  important  property  of  coagulability.  The  con- 
dition under  which  fibrin  coagulates  seems  to  be  that  of  stasis. 
Whenever  it  is  drawn  from  the  body,  or  in  the  vessels,  when 
circulation  becomes  arrested,  it  assumes,  after  a  variable  time, 
a  semi-solid  consistence.  The  cause  of  this  remarkable  phe- 
nomenon was  obscure  until  the  essay  of  Eichardson  on  the 
"  Cause  of  the  Coagulation  of  the  Blood"  appeared  in  1856. 
By  a  series  of  carefully  conducted  experiments,  this  observer 
demonstrated  that  the  blood  contains  a  small  quantity  of  free 
ammonia,  which  has  the  power  of  maintaining  the  fibrin  in  its 
liquid  condition.  This  ammonia  is  being  continually  devel- 


78  INTRODUCTION. 

oped  in  the  system,  is  taken  up  by  the  circulating  blood  and 
exhaled  by  the  lungs.  When  the  circulation  is  arrested  in  any 
part,  of  course  the  blood  takes  up  no  more  ammonia ;  and  as 
that  which  it  contained  is  gradually  exhaled  through  the 
tissues,  arrest  of  the  circulation  in  any  part  for  a  certain  time 
is  followed  by  coagulation  o/  the  fibrin.  When  blood  is 
drawn  from  the  vessels,  the  exhalation  of  ammonia  is  rapid, 
and  coagulation  takes  place  very  readily.  Some  other  chem- 
ical substances,  such  as  the  carbonate  of  soda,  have  the 
power  of  maintaining  the  fluidity  of  the  fibrin. 

Fibrin  does  not  coagulate  into  a  homogeneous  mass,  but 
forms  minute  microscopic  filaments,  or  fibrils,  which  after- 
wards contract  for  ten  or  twelve  hours,  so  that  the  clot  at 
the  end  of  that  time  is  much  smaller  than  immediately  after 
coagulation. 

We  recognize  only  as  fibrin  that  liquid  organic  principle 
which  coagulates  whenever  removed  from  its  natural  con- 
dition. By  coagulation  its  form  only  is  changed,  not  its 
weight,  and  we  must  consider,  therefore,  the  water  which  is 
contained  in  the  coagulated  mass  as  water  of  composition. 

Pure  coagulated  fibrin  is  a  grayish-white  substance,  com- 
posed of  microscopic  fibrils,  and  possessing  considerable 
strength  and  elasticity.  It  is  insoluble  in  water  and  in  the 
serum  of  the  blood,  but  dissolves  slowly  in  solutions  of  caustic 
alkalis.  It  swells,  assumes  a  jelly-like  consistence,  and  is 
finally  partially  dissolved  in  a  very  feeble  mixture  of  hydro- 
chloric acid  and  water.  Like  all  principles  of  this  class,  it 
decomposes  at  a  moderate  temperature  in  contact  with  the 
air  and  moisture. 

Organization  of  Fibrin. — The  question  of  the  organiza- 
tion of  accidentally  effused  and  coagulated  fibrin  has  occupied 
the  attention  of  pathologists  a  great  deal,  and  some  are  of 
opinion  that  it  is  capable  of  becoming  part  of  the  organized 
living  structure.  This  supposition  had  its  origin  in  an 
assumed  identity  between  fibrin  and  reparative  lymph,  or, 


ORGANIC   PRINCIPLES.  79 

as  it  is  sometimes  called,  coagulable  lymph,  which  repairs  losses 
of  tissue.  As  the  process  of  repair  of  parts  after  destruction 
must  be  considered  as  analogous  to,  and  almost  identical  with, 
ordinary  nutrition,  the  above  question,  which  is  so  important 
in  pathology,  is  one  of  great  physiological  interest. 

The  conditions  under  which  the  organization  of  fibrin  has 
been  assumed  to  have  taken  place,  are  in  clots  remaining 
after  vascular  extravasations,  and  fibrinous  exudations  upon 
inflamed  surfaces.  The  most  important  information  is  to  be 
derived  from  a  study  of  the  anatomical  characters  of  such 
effusions.  By  the  microscope,  and  all  means  of  investigation 
which  are  at  our  command,  it  is  impossible  to  distinguish  in 
these  effusions  any  thing  but  fibrin.  There  are  no  blood- 
vessels, nerves,  nor  any  anatomical  elements  which  would 
lead  us  to  suppose  them  capable  of  self-regeneration,  that 
distinctive  property  of  all  organized  tissues;  and,  in  addi- 
tion, these  are  never  developed.  The  changes  which  these 
effusions  undergo  are  retrograde  in  their  character ;  and  the 
fibrin,  if  it  be  not  absorbed,  remains  as  a  foreign  substance. 
The  fibrillation  which  takes  place  is  by  no  means  an  evidence 
of  even  commencing  organization;  for  in  effusions  into  the 
tissues  it  soon  disappears,  and  if  the  effusion  be  not  too  large, 
the  mass  breaks  down  and  is  finally  absorbed.  When,  on 
the  other  hand,  effusion  of  organizable  lymph  takes  place, 
the  process  is  very  different.  It  is  elaborated,  indeed,  rather 
than  effused;  first  appearing  as  a  homogeneous  fluid,  in 
which  fibro-plastic  nuclei,  then  fibres,  are  developed,  and  in 
some  instances  blood-vessels,  lymphatics,  and  nerves.  Ac- 
cording to  Robin,  plastic  lymph  does  not  even  contain  fibrin ; 1 
much  less  are  the  two  identical.  The  process  of  organization 
is  slow  and  gradual,  and  in  no  case  does  it  take  place  from 
the  blood,  or  elements  of  the  blood,  suddenly  or  accidentally 
effused. 

There   can  be  no   doubt  that  effused  and  coagulated 

1  Dictionnaire  de  NTSTEN,  par  KOBIN  et  LITTRE,  Paris,  1858.     "  Lymph  Plas- 
tique." 


80  INTRODUCTION. 

fibrin  is  incapable  of  organization ;  and  it  may  be  further 
stated  as  a  general  law  that  no  single  proximate  principle, 
nor  mere  mechanical  mixture  of  proximate  principles,  effused 
into  any  part  of  the  l>ody,  ever  acts  in  any  other  way  than  as 
a  foreign  substance. 

In  certain  instances  of  morbid  action,  effusions  take  place, 
either  on  the  surfaces  of  membranes,  or  between  two  opposing 
surfaces,  attaching  them  to  each  other  by  bridles  or  adhe- 
sions, which  actually  become  organized.  This  occurs  most 
frequently  in  serous  membranes,  and  the  structure  thus 
formed  is  entirely  different  from  coagulated  fibrin,  which  has 
no  connection  with  the  parts,  except  that  of  contiguity.  Both 
of  these  formations  have  been  included  in  the  term,  false 
membranes ;  but  Robin  makes  a  very  proper  distinction  be- 
tween them,  calling  the  one,  which  is  merely  coagulated 
fibrin,  like  the  membrane  of  croup,  false  membranes,  or 
pseudo-membranes  /  and  the  others  membranes  of  new  forma- 
tion, or  neo-meinbranes.  The  former  consist  simply  of  the 
fibrin,  which  nature  has  been  unable  to  remove  by  absorption  ; 
and  the  latter,  of  regularly  elaborated  anatomical  elements, 
endowed  with  the  properties  of  self-regeneration  common 
to  all  organized  structures. 

Origin  and  Function  of  Fibrin. — The  fibrin  of  the  blood 
has  its  direct  origin,  in  part  at  least,  from  the  albumen,  by 
the  catalytic  transformation  which  so  often  takes  place  in 
principles  of  this  class.  It  has  been  noticed  that  when  fibrin 
is  increased  in  the  blood,  albumen  is  diminished.  In  some 
experiments  presented  to  the  Society  of  Biology  of  Paris  by 
Dr.  Brown-Sequard,  it  was  shown  that  defibrinated  blood 
injected  into  the  arteries  of  a  criminal  just  after  death,  on 
being  returned  by  the  veins,  coagulated,  and  presented  a 
notable  quantity  of  fibrin.1  The  remote  origin  of  fibrin  is 
from  the  organic  nitrogenized  elements  of  food ;  which,  after 
having  undergone  the  catalytic  changes  incident  to  digestion, 

1  ROBIN  and  VERDEIL,  op.  «YM  tome  iii.,  p.  269. 


ORGANIC   PRINCIPLES.  81 

are  absorbed  and  transformed  into  albumen.  As  albumen 
exists  in  the  lymph  and  chyle,  it  is  probable  that  in  these 
fluids  fibrin  is  produced  in  the  same  way  as  in  the  blood. 

A  very  important  office  of  fibrin  is  to  give  coagula- 
bility to  the  blood.  This  will  be  taken  up  more  fully  here- 
after. At  present  we  need  only  say  that  by  virtue  of  this 
property  spontaneous  arrest  of  hemorrhage  after  division  or 
rupture  of  small  vessels  is  effected.  In  its  natural  liquid 
condition,  in  intimate  union  with  albumen  and  certain  inor- 
ganic matters  which  cannot  be  separated  from  it  without 
incineration,  fibrin  constitutes  one  of  the  two  peculiar  organic 
principles  of  the  plasma  of  the  blood.  It  is  brought  in  con- 
tact with  the  tissues  in  the  capillary  vessels,  and  probably 
takes  part  in  the  catalytic  changes  which  constitute  nutrition, 
being  transformed  into  the  peculiar  organic  element  of  each 
part.  In  this  way  it  disappears  forever  as  fibrin,  and  is  only 
discharged  from  the  body  after  the  tissue  has  undergone  the 
transformations  which  result  in  excrementitious  products. 

Simon,  Lehmann,  Bernard,  and  others  have  noticed  the 
remarkable  fact  that  the  blood  of  the  hepatic  and  renal  veins 
generally  contains  no  fibrin.  The  liver  and  kidneys  seem  to 
have  the  power  of  destroying  this  principle.  Its  transfor- 
mations in  these  organs  we  have  not  been  able  to  follow. 

Albumen. 

Albumen  is  found  in  the  blood,  lymph,  chyle,  intermus- 
cular  fluid,  secretions  of  serous  membranes,  and  in  small 
quantity  in  the  milk.  It  is  most  abundant  in  the  blood, 
constituting  the  most  important  organic  constituent  of  the 
plasma.  Its  proportion  has  been  estimated  in  the  various 
situations  in  which  it  is  found,  but,  as  in  the  case  of  fibrin, 
this  has  been  done  after  complete  desiccation,  and  the  results 
thus  obtained  are  far  from  representing  the  real  quantities. 
In  some  analyses  designed  to  give  the  quantity  of  moist  albu- 
men in  the  blood,  we  have  found  a  proportion  in  a  healthy 
specimen  of  329*82  parts  per  1000.  The  proportion  will 
6, 


82  INTRODUCTION. 

undoubtedly  be  found  to  vary  considerably  within  the  limits 
of  health,  and,  as  a  rule,  it  bears  an  inverse  ratio  to  the  quan- 
tity of  fibrin.  "No  constant  difference  in  the  quantity  of 
albumen  in  the  sexes  has  been  established.  The  quantity  is 
greater  in  the  well-nourished  and  vigorous,  than  in  anemic 
and  feeble  subjects. 

Albumen  is  found  in  the  organism  at  all  periods  of  life, 
existing  even  in  the  ovum. 

In  ultimate  composition  albumen  has  been  found  by 
chemists  to  differ  very  little,  if  at  all,  from  fibrin.  Like  the 
other  principles  of  this  class,  the  proportions  of  its  ultimate 
elements  are  indefinite. 

Albumen  may  be  extracted  from  the  fluids  in  which  it  is 
contained  by  simple  coagulation.  The  most  convenient 
method  of  separating  it  is  to  add  to  the  liquid  a  quantity  of 
absolute  alcohol,  and  immediately  filter.  In  operating  upon 
the  serum,  we  have  found  that  about  twice  its  volume  of 
alcohol  will  coagulate  all  the  albumen.  It  may  then  be 
collected  on  a  filter,  and  its  weight  will  represent  the  propor- 
tion of  this  principle  in  its  natural  condition. 

Like  fibrin,  albumen  is  naturally  fluid,  and  in  this  con- 
dition— and  this  condition  only — forms  the  important  organic 
principle  of  the  fluids  in  which  it  is  contained. 

Properties  of  Albumen. — Liquid  albumen  has  certain 
properties  which  serve  to  distinguish  it  from  other  principles 
of  the  same  class.  In  a  neutral  mixture  it  is  coagulated  com- 
pletely by  a  temperature  of  167°  Fahr.  The  same  result  fol- 
lows the  addition  of  the  strong  mineral  acids,  alcohol,  and  some 
of  the  metallic  salts.  It  is  distinguished  from  caseine  by 
the  fact  that  it  is  not  coagulated  by  the  vegetable  acids. 
Coagulated  albumen  is  a  grayish- white  substance,  always  com- 
bined with  inorganic  matter,  which  cannot  be  separated  with- 
out incineration,  insoluble  in  water,  but  soluble  in  a  weak  solu- 
tion of  a  caustic  alkali.  In  an  alkaline  solution  it  is  no  longer 
coagulable  by  heat.  Becqnerel  has  found  that  albumen  has 


ORGANIC  PRINCIPLES.  83 

the  property  of  deviating  the  plane  of  polarization  to  the 
left.  He  has  employed  a  polarizing  apparatus  like  the  one 
used  by  Biot  in  the  examination  for  sugar,  for  the  purpose 
of  estimating  the  quantity  of  albumen  in  a  watery  mixture, 
and  found  that  "each  minute  of  deviation  corresponds  to 
18  decigrammes  (29*77  grains)  of  dried  albumen  in  1,000 
cubic  centimetres  (1*76  pints)  of  water." 1  This  instrument  he 
calls  an  albuminimeter.  A  current  of  galvanism  passed 
through  a  mixture  containing  albumen  produces  coagulation, 
whicli  has  been  attributed  to  a  decomposition  of  certain  salts 
which  are  combined  with  it  and  maintain  its  fluidity. 

Some  organic  principles  almost  identical  with  albumen 
in  chemical  reactions,  are  found  to  possess  very  different 
vital  properties.  One  of  these  is  the  organic  principle  of 
the  gastric  juice,  which,  like  albumen,  is  coagulable  by 
heat,  alcohol,  and  the  metallic  salts,  but  exerts  a  peculiar 
and  distinctive  action  in  the  digestion  of  certain  articles  of 
food. 

Tests  for  Albumen. — As  a  pathological  condition,  albu- 
men sometimes  exists  in  the  urine,  and  it  becomes  important 
clinically  to  be  able  to  determine  this  fact  by  the  application 
of  tests.  These  require  certain  precautions  for  their  suc- 
cessful application.  They  depend  upon  its  property  of 
coagulation. 

If  a  solution  containing  albumen  be  exposed  to  heat 
in  a  test  tube,  as  the  temperature  rises  a  slight  cloudiness 
or  opacity  in  the  upper  part  of  the  liquid  occurs,  which 
gradually  extends  through  the  whole  mass,  until,  at  a 
temperature  of  about  167°,  a  precipitate  more  or  less  abun- 
dant is  produced,  which  is  entirely  insoluble.  If  albumen  be 
very  abundant,  the  whole  mass  may  become  solidified,  and 
we  may  have  all  shades  between  this  and  the  slight  opacity 
produced  by  a  very  minute  quantity.  In  the  latter  case 

1  BECQUEREL  and  RODIER,     Traite  de  Chimie  Pathologiqice,    Paris,  1854,  p.  53. 


84  INTRODUCTION. 

coagulation  is  not  complete  until  the  liquid  has  been  brought 
to  the  boiling  point.  It  must  be  remembered,  however,  that 
albumen  is  not  coagulated  by  heat  in  an  alkaline  solution. 
In  testing  the  urine  for  albumen  by  heat,  if  the  liquid  be 
alkaline  it  must  be  neutralized  with  a  little  acetic  acid ;  other- 
wise there  will  be  no  coagulation,  even  if  albumen  be  present 
in  abundance.  There  may  also  arise  a  source  of  error  from 
the  precipitation  by  heat  of  an  excess  of  earthy  phosphates. 
This  precipitate  is  distinguished  from  albumen  by  the  fact 
that  it  is  dissolved  by  a  few  drops  of  hydrochloric  acid,  while 
coagulated  albumen  is  not  changed.  Coagulated  albumen 
in  urine  is  redissolved  by  the  addition  of  a  little  potash, 
which  has  no  effect  upon  an  opacity  produced  by  the 
phosphates. 

Another  test  is  the  addition  to  the  suspected  solution  of 
a  strong  mineral  acid ;  when,  if  albumen  be  present,  coagu- 
lation will  take  place.  There  is  only  one  source  of  error  in 
the  application  of  this  test  to  the  urine.  If  the  urates  be 
present  in  very  large  quantity,  we  may  have  a  deposit  of 
uric  acid,  giving  an  opacity  something  like  that  produced 
by  coagulated  albumen.  This  error  may  be  avoided  by 
adding  an  excess  of  nitric  acid,  which  will  clear  up  the  mix- 
ture if  the  deposit  be  due  to  the  presence  of  urates,  but  has 
no  effect  upon  albumen.  In  such  a  case,  also,  no  turbidity 
is  produced  by  heat.  "When  uric  acid  is  deposited,  the 
turbidity  makes  its  appearance  more  slowly  than  when  albu- 
men is  present  Various  acid  mixtures  have  been  proposed 
as  tests  for  albumen,  but  they  seem  to  possess  no  advan- 
tages over  nitric  acid,  which  is  the  one  most  generally  em- 
ployed. 

The  tests  by  heat  and  nitric  acid  are  sufficient  to  deter- 
mine the  presence  or  absence  of  albumen  in  any  clear 
fluid,  if  applied  with  the  precautions  above  indicated.  We 
may  employ,  however,  coagulation  by  alcohol,  or  the  albu- 
minimeter  of  Eecquerel ;  but  the  latter,  like  the  saccharom- 
eter  of  Biot  and  Soleil,  is  little  used  on  account  of  the 


ORGANIC  PRINCIPLES.  85 

expense  of  the  instrument,  and  a  certain  dexterity  which,  is 
necessary  for  its  exact  application. 

Origin  and  Function  of  Albumen. — The  albumen  of  the 
blood  has  its  origin  from  a  catalytic  transformation  of  the 
products  of  digestion  of  the  albuminoid  elements  of  food. 
It  forms  the  great  organic  nutrient  element  of  the  blood.  As 
we  have  already  seen,  it  seems  to  be  used  in  the  formation 
of  the  fibrin.  In  nutrition,  it  undergoes  catalytic  transfor- 
mations which  result  in  the  peculiar  organic  principles  of  the 
various  tissues.  In  the  circulating  blood  there  seems  to  be 
a  union  of  the  fibrin  and  albumen  which  is  necessary  to  the 
nutritive  properties  of  the  latter.  Bernard  has  shown1  that 
the  albumen  of  white  of  egg  injected  into  the  veins  of  an 
animal  is  incapable  of  assimilation,  and  is  therefore  rejected 
by  the  kidneys.  The  same  result  follows  the  injection  of 
fresh  serum,  even  from  an  animal  of  the  same  species ;  but 
the  blood  itself,  containing  both  albumen  and  fibrin,  can  be 
injected  without  the  appearance  of  albumen  in  the  urine,  show- 
ing that  in  this  state  it  is  capable  of  being  used  in  nutrition. 

In  the  passage  of  the  blood  through  the  liver,  it  has  been 
found  that  a  small  quantity  of  albumen  disappears ;  but,  as 
in  the  case  of  fibrin,  we  have  not  been  able  to  follow  its 
transformations.  With  the  exception  of  the  minute  quantity 
which  is  discharged  in  the  milk  during  lactation,  albumen  is 
never  discharged  from  the  body  in  health.  After  being 
appropriated  by  the  tissues  in  the  process  of  nutrition,  it 
undergoes  changes  in  the  wearing  out  of  the  system,  which 
convert  it  into  excrementitious  matter. 

Albuminose. 

This  principle  is  intermediate  between  the  organic  nitro- 
genized  elements  of  food  and  the  albumen  of  the  blood.  It 
is  found  in  the  blood  in  very  small  quantity  after  digestion, 

1  BERNARD,  Lemons  sur  les  Proprietes  Physiologiques  et  les  Alterations  Pa* 
thologiquto  den  Liquidcs  de  VOrganisme,  Paris,  1859,  tome  i.,  p.  467. 


86  INTRODUCTION. 

almost  immediately  undergoing  transformation  into  albu- 
men. It  is  also  contained  in  the  stomach  and  small  intestines 
during  digestion.  It  is  naturally  fluid,  like  albumen  and 
fibrin. 

In  its  behavior  to  reagents,  albuminose  presents  certain 
differences  from  albumen.  It. is  coagulated  by  alcohol  and 
many  metallic  salts,  but  is  not  coagulable  by  heat,  and  only 
imperfectly  by  nitric  acid.  It  is  coagulated  by  a  small  quan- 
tity of  acetic  acid,  but  the  coagulum  is  dissolved  in  an  excess 
of  this  agent,  the  latter  peculiarity  distinguishing  it  from 
caseine,  which  is  coagulated  by  acetic  acid  in  any  quantity. 
Mialhe  states  that  albuminose  is  more  endosmotic,  or  passes 
through  membranes  with  much  greater  facility  than  albumen, 
which  he  says  is  absolutely  non-endosmotic.  This  property 
favors  its  introduction  into  the  blood. 

Albuminose  has  its  origin  from  the  organic  nitrogenized 
elements  of  food,  which  are  not  only  liquefied  by  the  diges- 
tive fluids,  but  undergo  a  catalytic  transformation  into  this 
substance.  By  virtue  of  its  endosmotic  properties,  it  passes 
into  the  blood-vessels,  and  is  there  converted  into  albumen. 
Mialhe,  who  first  described  this  substance  under  the  name 
of  albuminose,  has  shown  that,  injected  into  the  veins  of  an 
animal,  it  becomes  assimilated,  and  does  not  pass  away  in 
the  urine.1 

Caseine. 

This  organic  principle  is  peculiar  to  the  milk,  and  there- 
fore exists  in  the  body  only  during  lactation.  Like  fibrin 
and  albumen,  it  is  naturally  fluid. 

Caseine  may  be  easily  extracted  by  the  following  process, 
which  is  recommended  by  Robin  and  Yerdeil.2  "  "We  add 
to  the  milk  a  few  drops  of  acetic  acid,  which  precipitates  the 
caseine  accompanied  by  the  fats.  The  coagulum  separated 

1  MIALHE,      Chimie  Appliquee  d  la  Physiologic,    Paris,  1856,  p.  125. 

2  Op.  cit.,  tome  iii.,  p.  341. 


OEGANIC   PEINCIPLES.  87 

from  the  liquid,  then  washed,  is  redissolved  in  a  solution  of 
carbonate  of  soda ;  this  solution  separates  from  the  fat  which 
floats  on  the  top,  and  can  be  completely  removed  at  the  end 
of  twelve  hours  of  repose.  The  liquid  thus  freed  from  fat  is 
acidified  by  a  few  drops  of  hydrochloric  acid,  and  the  caseine 
is  precipitated  perfectly  pure."  Obtained  by  this  process,  it 
is  perfectly  white,  and  insoluble  in  water,  resembling  pot 
cheese. 

Caseine  has  certain  marked  properties  by  which  it  is  dis- 
tinguished from  albumen.  It  is  not  coagulable  by  heat; 
is  coagulable  by  the  feeble  vegetable,  as  well  as  the  mineral 
acids,  and  by  rennet.  This  latter  substance  is  obtained  from 
the  fourth  stomach,  or  abomasus,  of  sucking  ruminating  ani- 
mals, and  is  the  milk  almost  reduced  to  caseine,  and  mixed 
with  the  gastric  fluids.  It  is  salted  and  dried,  and  in  this  con- 
dition used  in  making  cheese.  Added  to  the  milk  in  the  pro- 
portion of  fifteen  to  twenty  grains  to  a  quart,  it  produces  com- 
plete coagulation.  According  to  Robin  and  Yerdeil,  caseine 
is  precipitated  by  the  metallic  salts,  with  which  it  forms  com- 
binations not  to  be  distinguished  from  like  combinations  of 
albumen.1  It  is  a  curious  fact  that  caseine  is  sometimes 
coagulated  almost  instantly  during  thunder  storms.  This 
phenomenon  we  cannot  fully  explain;  but  the  immediate 
cause  of  the  coagulation  is  the  transformation  of  some  of  the 
sugar  of  milk  into  lactic  acid.  Caseine  retains  its  fluidity 
in  the  milk  by  union  with  the  carbonate  of  soda ;  and  when 
coagulated  spontaneously,  it  may  be  restored  to  its  liquid 
condition  by  the  addition  of  this  salt,  which  does  not  render 
the  fluid  alkaline,  "but  seems  to  enter  into  combination  with 
the  organic  substance. 

Caseine  has  its  origin  in  the  albumen  of  the  blood,  by  a 
catalytic  process  which  takes  place  in  the  mammary  glands. 
In  its  liquid  condition  it  constitutes  the  important  organic 
element  of  the  milk.  It  is  taken  into  the  stomach  of  the 

1  Loe.  tit. 


88  INTRODUCTION. 

infant,  converted  into  albuminose,  which  it  resembles  very 
closely,  and  absorbed  by  the  blood,  where  it  is  converted  into 
fibrin  and  albumen,  and  contributes  to  the  nutrition  of  the 
system.  At  this  period  it  constitutes  almost  the  only  nitro- 
genized  element  of  food.  It  is  the  only  proximate  principle 
of  this  class,  with  the  exception  of  a  little  mucosine  and  the 
coloring  matter  of  the  urine  and  bile,  which  is  discharged 
from  the  body  in  health. 

Pancreatine. 

This  is  the  organic  principle  peculiar  to  the  pancreatic 
juice.  Bernard  was  the  first  to  describe  its  properties,  both 
chemical  and  physiological.1  Before  the  appearance  of  his 
admirable  monogragh  on  the  pancreas  it  was  confounded  with 
albumen;  but  we  shall  see  that  it  possesses  properties  by 
which  it  may  be  distinguished  as  readily  as  caseine. 

Pancreatine  exists  in  the  pancreatic  juice  in  large  quan- 
tity. It  is  naturally  fluid,  but  very  viscid.  It  is  coagulated 
by  heat,  the  strong  acids,  and  alcohol,  but  is  unaffected  by 
the  feeble  vegetable  acids.  It  is  distinguished  from  albumen 
by  the  fact  that  it  is  completely  coagulated  by  an  excess  of 
sulphate  of  magnesia.  Its  distinctive  physiological  character 
is  its  powerful  digestive  action  upon  certain  elements  of  food, 
and  its  property  of  forming  an  instantaneous,  complete,  and 
very  fine  emulsion  with  liquid  fats. 

Pancreatine  has  its  origin  from  the  albumen  of  the  blood 
by  a  catalytic  change  which  takes  place  in  the  pancreas.  It 
gives  to  the  pancreatic  juice  its  digestive  properties.  , 

Pepsin. 

Pepsin  is  the  organic  principle  of  the  gastric  juice.  It 
is  hardly  to  be  distinguished  from  albumen,  except  by  its  phys- 
iological action  in  digestion.  The  principle  which  has  been 
extracted  by  various  processes  from  the  mucous  membrane 

'BERNARD,     Hemoire  sur  le  Pancreas*   Paris,  1858. 


ORGANIC   PRINCIPLES.  89 

of  the  stomach,  particularly  after  commencing  putrefaction, 
cannot  be  regarded  as  pure  pepsin.  It  is  undoubtedly  neces- 
sary to  the  digestive  action  of  the  gastric  juice,  which  loses 
its  physiological  properties  when  this  substance  has  been 
coagulated  by  heat  and  separated  by  filtration.  Its  properties 
will  be  more  fully  considered  under  the  head  of  digestion, 

Mucosine. 

This  is  the  organic  principle  of  the  general  secretion 
of  mucous  membranes,  presenting,  however,  some  differ- 
ences in  different  situations.  In  its  general  properties  it 
closely  resembles  albumen ;  indeed,  what  is  generally  taken 
as  the  type  of  pure  albumen,  the  white  of  egg,  should  strictly 
be  called  mucosine,  as  it  is  the  secretion  of  the  mucous  mem- 
brane of  the  Fallopian  tubes,  and  almost  identical  with  some 
specimens  of  pure  mucus,  such  as  the  secretion  at  the  neck 
of  the  uterus  during  gestation.  It  is  imperfectly  coagulated 
by  heat,  but  is  thrown  down  by  strong  acids  and  the  metal- 
lic salts.  It  is  formed  from  the  blood  by  the  mucous  follicles ; 
and,  as  a  small  quantity  is  discharged  from  the  body,  forms 
one  exception  to  the  general  law  that  organic  nitrogenized 
principles  are  never  discharged  from  the  body  in  health. 

Semi-solid  or  Solid  Principles. 

Most  of  the  liquid  elements  which  we  have  just  considered 
have  been  found  to  be  connected,  directly  or  indirectly,  with 
the  nutrition  of  the  body.  Those  which  we  now  have  to 
consider  are  all  directly  formed  from  the  organic  principles 
of  the  blood,  and  constitute  the  organic  portion  of  the  econ- 
omy. Here  is  found  to  be  the  final  destination  of  fibrin  and  al- 
bumen in  nutrition  ;  for  the  organic  principles  constitute  the 
vital  elements  of  all  the  tissues,  and  are  nourished  exclusively 
by  these  elements  of  the  blood.  We  include  here  the  blood 
corpuscles,  which  must  be  regarded  as  organized  bodies, 
nourished  like  any  of  the  tissues.  The  following  are  the  prin- 


90  INTRODUCTION.  * 

ciples  in  this  group  which  are  well  established,  and  have  been 
studied  to  a  greater  or  less  extent : 

* 

Globuline, 

Crystalline, 

Musculyne, 

Osteine, 

Cartilagine, 

ElastiGine, 

Keratine. 

Gldbuline. — This  is  a  semi-solid  organic  principle,  con- 
stituting  the  greater  portion  of  the  blood  corpuscles.  It  is 
soluble  in  water,  from  which  it  is  coagulated  by  a  tempera- 
ture a  little  below  the  boiling  point.  Excepting  that  when 
mixed  with  water  it  requires  a  much  higher  temperature 
for  its  coagulation,  it  has  nearly  the  same  properties  as 
albumen. 

Like  the  rest  of  these  principles,  it  exists  in  a  state  of 
intimate  molecular  union  with  inorganic  elements;  but, 
exceptionally  in  this  case,  is  united  with  a  small  quantity  of 
fat.  In  this  condition  it  goes  to  form  the  organized  structure 
of  the  blood  corpuscles. 

Crystalline. — This  is  a  semi-solid  organic  principle, 
peculiar  to  the  crystalline  lens.  It  presents  most  of  the 
characters  of  globuline,  but  is  coagulated  at  a  little  lower 
temperature,  though  higher  than  is  required  to  coagulate 
albumen. 

Musculine. — This  semi-solid  organic  principle  is  peculiar 
to  the  muscular  tissue.  It  is  immediately  dissolved  at  the 
ordinary  temperature  by  a  mixture  of  ten  parts  of  water  with 
one  of  hydrochloric  acid.  It  may  be  precipitated  from  this 
solution  by  neutralizing  the  acid,  and  the  precipitate  is  re- 
dissolved  by  an  alkali.  It  is  always  united  with  a  consider- 


OEGANIC   PEINCIPLES.  91 

able  quantity  of  inorganic  salts,  in  which  the  phosphates 
predominate. 

Musculine,  in  combination  with  inorganic  substances, 
goes  to  form  the  muscles ;  but  in  addition,  is  interesting  as 
being  by  far  the  most  important  and  abundant  nitrogenized 
element  of  food.  It  is  the  great  source  of  the  fibrin  and 
albumen  of  the  blood  of  man  and  of  the  carnivorous  animals. 

Osteine. — This  organic  principle,  naturally  solid,  is  pecu- 
liar to  the  bones.  If  the  earthy  matter  of  bone  be  dissolved 
out  with  dilute  hydrochloric  acid,  the  residue  is  nearly  pure 
osteine.  By  boiling  with  water  it  is  transformed  into  gelatine^ 
a  soluble  substance  differing  in  many  respects  from  osteine. 
According  to  the  experiments  of  Magendie,  fresh  bones 
possess  considerable  nutritive  power,  which  is  entirely  de- 
stroyed by  prolonged  boiling.  It  enters  into  combination 
with  large  quantities  of  earthy  salts,  to  form  the  bones. 

Cartilagine. — This  principle  holds  the  same  relation  to 
cartilage  as  osteine  does  to  bone.  By  prolonged  boiling  it 
is  transformed  into  a  substance  resembling  gelatine,  called 
by  Miiller  chondrine.  This  presents  many  points  of  difference 
from  gelatine,  which  renders  it  probable  that  the  transfor- 
mation of  cartilage  into  bone,  does  not  merely  consist  in  the 
deposition  of  calcareous  matter,  but  also  the  substitution  of  a 
new  organic  principle. 

JElasticine. — This  is  the  organic  principle  of  the  yellow 
elastic  tissue  and  the  investing  membrane  of  the  muscular 
fibres.  According  to  Robin  and  Yerdeil  it  is  slowly  dissolved 
by  sulphuric,  nitric,  and  hydrochloric  acids,  and  these  solu- 
tions, diluted  with  water,  are  not  precipitated  by  alkalis.  It 
is  possessed  of  great  strength  and  elasticity. 

Keratine. — This  is  an  organic  principle,  found  in  the  nails 
and  hair,  about  which  we  know  very  little.  It  differs  from 


92  INTRODUCTION. 

the  other  principles  in  the  fact  that  it  is  not  dissolved,  but 
decomposed  by  potash,  giving  off  ammoniacal  vapor. 

Coloring  Matters. 

These  substances  have  b§eii  classed  with  the  organic 
nitrogenized  principles,  from  the  fact  that  they  contain  ni- 
trogen ;  but  they  do  not  seem  to  be  endowed  with  the  vital 
properties  which  characterize  this  class,  with  the  exception 
perhaps  of  hematine  and  melanine.  As  a  peculiarity  of 
chemical  constitution,  they  all  contain  iron,  which  is  molec- 
ularly  united  with  their  other  elements.  The  following  are 
the  principles  of  this  group : 

Hcematine, 
Melanine^ 
JBiliverdine, 
Urrosacine. 

Hcematine. — This  is  the  red  coloring  matter  of  the  blood, 
and  exists,  intimately  united  with  globuline,  in  the  blood 
corpuscles.  The  iron  which  it  contains  can  be  readily  dem- 
onstrated, even  in  a  single  drop  of  blood,  by  the  following 
process :  To  a  small  quantity  of  blood  in  a  watch-glass  we 
add  a  drop  of  nitric  acid,  then  evaporate  slowly  over  a  lamp, 
when  fumes  of  nitrous  acid  are  driven  off,  the  iron  takes 
oxygen  and  is  converted  into  a  per-oxide.  If  we  then  add  a 
drop  of  the  sulpho-cyanide  of  potassium,  we  produce  the 
characteristic  red  color  of  the  sulpho-cyanide  of  iron.  Sep- 
arated from  the  blood,  hsematine  is  soluble  in  ether  and  boil- 
ing alcohol,  but  insoluble  in  water  and  in  acids. 

"We  do  not  exactly  understand  the  mode  of  formation  of 
haematine,  but  pathology  teaches  us  that  it  is  an  essential 
principle  of  the  blood.  In  certain  cases  of  anaemia,  when 
there  is  extreme  pallor  and  consequently  deficiency  of  hema- 
tine, the  administration  of  iron  in  any  form  induces  the  for- 
mation of  this  substance,  restores  the  normal  constitution  of 


COLORING  MATTEES.  93 

the  circulating  fluid,  and  relieves  the  general  effects  of  the 
deficiency  of  coloring  matter;  an  effect  which  cannot  be 
produced  by  the  most  nutritious  articles  of  food.  Hsematine 
is  probably  destroyed  in  the  organism,  and  furnishes  material 
for  the  formation  of  the  other  coloring  matters. 

Melanine. — This  substance  resembles  hsematine,  contain- 
ing, however,  a  smaller  proportion  of  iron.  It  is  of  a  brown- 
ish color,  and  is  found  in  all  parts  of  the  body  where  pigment 
exists ;  such  as  the  choroid,  iris,  hair,  or  epidermis.  It  exists 
in  the  form  of  granulations,  either  free  or  enclosed  in  epithe- 
lial cells.  In  all  probability  it  is  formed  by  a  transformation 
of'hematine. 

Biliverdine. — This  is  a  greenish-yellow  coloring  matter 
peculiar  to  the  bile.  Extracted  from  the  bile,  it  is  insoluble 
in  -water,  but  soluble  in  alcohol  or  ether.  It  contains  iron  in 
nearly  the  same  proportion  as  haematine. 

Biliverdine  is  formed  from  haematine,  enters  into  the  con- 
stitution of  the  bile,  is  discharged  into  the  small  intestine, 
and,  after  undergoing  certain  modifications,  is  discharged 
from  the  body  in  the  feces. 

Urrosacine. — This  is  the  principle  which  gives  the  amber 
color  to  the  urine.  After  extraction,  it  is  insoluble  in  water, 
but  soluble  in  alcohol  or  ether.  It  exists  in  the  urine  in  very 
small  quantity,  and  is  formed  in  the  kidney,  in  all  probability 
at  the  expense  of  the  haematine.  Urrosacine  and  biliverdine 
are  the  two  coloring  matters  discharged  from  the  body. 

Summary. — A  review  of  the  individual  properties  of  the 
organic  nitrogenized  principles  shows  great  differences  in  their 
physiological,  and  very  slight  differences  in  their  purely 
chemical  characters.  It  is  a  fact  too  apparent  to  require 
argument,  that  their  chemical  history  is  of  little  importance 
compared  to  a  study  of  their  vital  properties.  In  fact  re- 
searches into  their  ultimate  composition,  with  the  excep- 


94:  INTRODUCTION. 

tion  that  they  have  shown  them  all  to  contain  nitrogen,  are 
almost  without  value.  Without  exception  they  are  all  in  a 
state  of  intimate  molecular  union  with  inorganic  matter,  and 
in  this  union  inorganic  compounds  become  endowed  with 
life  ;  that  is,  the  inorganic  parts  of  the  body,  as  the  calcareous 
elements  of  bone,  taken  up  ty  the  blood  with  the  worn-out 
organic  principles  and  undergoing  constant  waste,  are  capa- 
ble of  self-regeneration. 

The  vitality  thus  imparted  to  inorganic  matters,  and  the 
fact  that  neither  the  organic  nor  inorganic  elements  are  alone 
capable  of  engaging  in  the  phenomena  of  life,  cannot  le  too 
fully  insisted  upon.  Both  are  taken  into  the  body  as  food, 
are  digested,  assimilated,  and  finally  discharged,  always  in 
combination;  the  organic  principles  changed,  and  converted 
into  excrementitious  substances,  and  the  inorganic  principles 
unchanged. 

The  readiness  with  which  the  organic  principles  are  con- 
verted one  into  the  other  by  catalysis  must  also  be  appre- 
ciated, as  well  as  the  constant  operation  of  this  process  in 
all  the  phenomena  of  life.  Even  albumen,  taken  in  as  food, 
must  be  converted  into  albuminose,  and  again  into  albumen, 
before  it  is  capable  of  building  up  the  tissues ;  and  all  the 
nitrogenized  articles  of  food  are  converted  into  the  same  sub- 
stance, regenerating  the  blood,  and  through  it  the  body. 

In  the  economy  we  find  two  great  divisions  of  organic 
elements :  one,  which,  is  nutritive,  and  the  other,  which 
forms  the  great  part  of  the  tissues.  By  simple  contact,  the 
plastic,  or  nutritive,  principles  are  mysteriously  converted 
into  the  varied  elements  of  the  organism,  and  take  writh  them 
the  inorganic  elements  necessary  to  the  proper  constitution 
of  the  parts. 

It  is  only  with  a  just  appreciation  of  these  general  princi- 
ples that  we  are  able  to  study  intelligently  the  special  functions 
of  respiration,  circulation,  digestion,  absorption,  secretion  and 
excretion,  which  are  all  tributary  to  the  complicated  function 
of  nutrition. 


CHAPTEE  I. 

THE   BLOOD. 

General  considerations — Transfusion — Quantity — Physical  characters — Opacity- 
Temperature — Specific  gravity — Color — Anatomical  elements  of  the  blood — 
Eed  corpuscles — Chemical  characters  of  red  corpuscles — Development  of  red 
corpuscles — Formation  of  red  corpuscles — Leucocytes,  or  white  corpuscles — 
Development  of  leucocytes. 

IN  all  ages,  even  before  physiology  became  known  as  a  dis 
tinct  science,  the  importance  of  the  blood  in  the  animal 
economy  has  been  recognized ;  and  with  the  progress  of 
knowledge  this  great  nutritive  fluid  has  been  shown  to  be 
more  and  more  intimately  connected  with  the  phenomena  of 
life.  It  is  now  known  to  be  the  most  abundant  and  highly 
organized  of  the  animal  fluids;  providing  materials  for  the 
regeneration  of  all  parts,  without  exception,  receiving  the 
products  of  their  waste  and  conveying  them  to  proper  organs, 
by  which  they  are  removed  from  the  system.  These  processes, 
on  the  one  hand,  require  constant  regeneration  of  its  constit- 
uents, and  on  the  other,  constant  purification  by  the  removal 
of  effete  matters.  As  it  has  been  found  desirable  to  preface 
our  study  of  general  physiology  with  a  history  of  proximate 
principles,  showing  the  chemical  and  vital  properties  of 
what  maybe  considered  as  the  permanent  constituents  of  the 
body,  so  before  considering  individual  functions,  all  of  which 
bear  finally  on  the  great  process  of  nutrition,  we  should 
have  an  accurate  knowledge  of  the  anatomy  and  chemistry 


96  THE  BLOOD. 

of  what  is  most  appropriately  called  the  great  nutritive  fluid. 
It  has  been  said  that  all  parts  are  dependent  on  the  blood  for 
nourishment.  Those  tissues  in  which  the  processes  of  nutri- 
tion are  active  are  supplied  with  blood  by  vessels ;  but  some 
less  highly  organized,  like  the  epidermis,  hair,  cartilage,  etc., 
which  are  sometimes  called  ^xtra-vascular  because  they  are 
not  penetrated  by  blood-vessels,  are  none  the  less  dependent 
upon  the  fluid  under  consideration;  imbibing,  as  they  do, 
nourishment  from  the  blood  of  adjacent  parts. 

It  must  be  remembered  that  in  nutrition  the  tissues 
are  active,  selecting,  appropriating,  and  modifying  material 
which  is  simply  furnished  by  the  blood  ;  and  as  the  real  vital 
force  which  governs  these  processes  resides  in  the  tissues,  ten- 
dencies of  the  system,  such  as  the  tubercular,  scrofulous,  or 
cancerous  diatheses,  which  lead  to  disordered  nutrition,  must 
have  their  seat  in  the  solids,  and  not  in  the  circulating  fluid. 
The  first  cause  of  these  conditions  may  lie  in  a  disordered 
state  of  the  blood,  from  bad  nourishment,  from  the  introduc- 
tion of  poisons,  such  as  malaria,  or  the  emanations  from  per- 
sons affected  with  contagious  diseases,  and  under  some  cir- 
cumstances the  elimination  of  these  poisons  may  be  effected 
through  the  blood ;  but  when  they  exist  in  the  blood,  they 
either  become  fixed  in  the  system,  or  are  thrown  off.  We 
must  regard  most  of  the  morbid  actions  which  are  dependent 
on  diathesis,  as  the  result  of  a  vice  in  the  tissue  itself,  not  the 
blood  with  which  it  is  supplied.  It  is  none  the  less  essential 
to  health,  however,  that  the  blood  should  have  its  proper 
constitution. 

The  final  importance  of  the  blood  in  the  processes  of 
nutrition  is  evident ;  and  in  animals  in  which  nutrition  is 
active,  death  is  the  immediate  result  of  its  abstraction  in  large 
quantity.  Its  immediate  importance  to  life  can  be  beauti- 
fully demonstrated  by  experiments  upon  inferior  animals. 
If  we  take  a  small  dog,  introduce  a  canula  through  the  right 
jugular  vein  into  the  right  side  of  the  heart,  adapt  to  it  a 
syringe,  and  suddenly  withdraw  a  great  part  of  the  blood 


TRANSFUSION.  97 

from  the  circulation,  immediate  suspension  of  all  the  vital 
processes  is  the  result.  If  we  then  return  the  blood  to  the 
system,  the  animal  is  as  suddenly  revived.1  To  perform  this 
experiment  satisfactorily,  we  must  accurately  adjust  the  ca- 
pacity of  the  syringe  to  the  size  of  the  animal.  Carefully 
performed,  it  is  very  striking. 

Trcwsfusion.— Certain  causes,  one  of  which  is  diminution 
in  the  force  of  the  heart  after  copious  hemorrhage,  prevent  the 
escape  of  all  the  blood  from  the  body,  even  after  division  of 
the  largest  arteries ;  but  after  the  arrest  of  the  vital  functions 
which  follows  copious  discharges  of  this  fluid,  life  may  be  re- 
stored by  the  injection  into  the  vessels  of  the  same  blood,  or 
the  fresh  blood  of  another  animal  of  the  same  species.  This 
observation,  which  was  first  made  on  the  inferior  animals, 
has  been  applied  to  the  human  subject ;  and  it  has  been  as- 
certained that  in  patients  sinking  under  hemorrhage,  the  in- 
troduction of  even  a  few  ounces  of  fresh  blood  will  restore 
the  vital  forces  for  a  time,  and  sometimes  permanently.  The 
operation  of  transfusion,  which  consists  in  the  introduction 
of  the  blood  of  one  individual  into  the  vessels  of  another,, 
was  performed  upon  animals  in  the  middle  of  the  seven- 
teenth century,  and  was  soon  after  attempted  in  the  human 
subject.  So  great  was  the  enthusiasm  with  which  some  re- 
garded these  experiments,  that  it  was  even  thought  possible 
to  effect  a  renewal  of  youth  by  the  introduction  of  young 
blood  into  the  veins  of  old  persons ;  and  it  was  also  proposed 
to  cure  certain  diseases,  such  as  insanity,  by  an  actual  renewal 
of  the  circulating  fluid.  These  ideas  were  not  without  ap- 
parent foundation.  It  was  stated  in  1667,  that  a  dog,  old  and 
deaf,  had  his  hearing  improved  and  was  apparently  rejuve- 
nated by  transfusion  of  blood  from  a  young  animal.  A  year 
later  Denys  and  Emmerets  published  the  case  of  a  maniac 
who  was  restored  to  health  by  the  transfusion  of  eight  ounces 

1  BERNARD,     Lemons  sur  les  Liquides  de  V  Organisme,    tome  i.,  p.  44. 

7 


98  THE    BLOOD. 

of  blood  from  a  calf;  and  another  case  was  reported  of  a  man 
who  was  cured  of  leprosy  by  the  same  means.  But  a  reac- 
tion followed.  The  case  of  insanity,  which  was  apparently 
cured,  suffered  a  relapse,  and  the  patient  died  during  a 
third  attempt  at  transfusion.1  It  is  almost  unnecessary  to 
say  that  these  extravagant  ^expectations  were  not  realized. 
In  fact  some  operations  were  followed  by  such  disastrous  con- 
sequences, that  the  practice  wras  forbidden  by  law  in  Paris  in 
1668,  and  soon  fell  into  disuse. 

Transfusion,  with  more  reasonable  applications,  was  re- 
vived in  the  early  part  of  this  century  (1818)  by  Blundell, 
who,  with  others,  demonstrated  its  occasional  efficacy  in  des- 
perate hemorrhage,  and  in  the  last  stages  of  some  diseases, 
especially  cholera.  There  are  now  quite  a  number  of  cases  on 
record  where  life  has  been  saved  by  this  means ;  and  often- 
times, when  the  result  has  not  been  so  happy,  the  fatal  event 
has  been  considerably  delayed.  In  a  case  which  occurred  at 
'New  Orleans,  when  the  system  was  prostrated  by  an  obscure 
affection  and  life  became  nearly  extinct,  about  seven  ounces 
of  blood  in  all  were  transfused  in  three  operations,  within  two 
hours,  with  the  palpable  effect  of  prolonging  life  for  from 
twelve  to  sixteen  hours.'  Berard  had  collected  from  various 
sources  thirteen  observations  of  hemorrhage,  which  wrould  have 
been  fatal,  in  which  life  was  permanently  restored  by  the 
injection  of  a  few  ounces  of  healthy  human  blood.  In  all 
but  two  of  these  cases  the  hemorrhage  was  uterine.3 

1  Philosophical  Transactions,  London,  1668,  p.  710,  et  seq. 

*  In  this  case  the  patient  suffered  extreme  prostration  after  the  delivery  of  a 
seven  and  a  half  months'  child.  This  continued  for  a  few  days,  and  at  the  time 
of  transfusion,  the  pulse  was  140  and  very  feeble ;  respirations  six  to  eight  per 
minute ;  nostrils  compressed  at  each  inspiration ;  surface  cool ;  countenance  Hip- 
pocratic,  and  the  coma  so  profound  that  the  patient  could  not  be  aroused.  After 
each  transfusion  the  lips  became  more  florid,  the  nostrils  dilated  in  inspiration, 
and  the  surface  became  warmer.  The  patient  lived  twenty-four  hours  after  the 
first  operation.  The  blood  was  taken  from  the  arm  of  a  healthy  male  and  trans- 
fused immediately  into  the  median  cephalic  vein. 

3  BERARD,  Cours  de  Physiologic,  Paris,  1851,  tome  iii.,  p.  219,  et  scq. 


TEANSFUSION.  99 

Since  this  time  a  great  many  experiments  on  transfusion 
in  animals  have  been  performed,  with  very  interesting  results. 
Prevost  and  Dumas l  have  shown,  that  while  an  animal  may 
be  restored  after  hemorrhage  by  the  transfusion  of  defibrinated 
blood,  no  such  effect  follows  the  introduction  of  the  serum ; 
showing  that  the  vivifying  influence  in  all  probability  resides 
in  the  corpuscles.  These  observers  have  also  shown,  that 
though  an  animal  may  be  temporarily  revived  by  the  injection 
of  defibrinated  blood  from  an  animal  of  a  different  species, 
death  follows  the  operation  in  a  few  days.3  Brown-Sequard 
has  shown  that  in  parts  detached  from  the  body,  after  nervous 
and  muscular  irritability  have  disappeared,  these  properties 
may  be  restored  for  a  time  by  the  injection  of  fresh  blood.3 
lie  also  reports  a  curious  experiment  in  which  blood  was 
passed  from  a  living  dog  into  the  carotid  of  a  dog  just  dead 
from  peritonitis.  The  animal  was  so  far  revived  as  to  sustain 
himself  on  his  feet,  wag  his  tail,  etc.,  and  died  a  second  time, 
twelve  and  a  half  hours  after.  In  this  experiment  insufflation 
was  employed  in  addition  to  the  transfusion.4 

It  may  then  be  considered  established,  that  in  animals, 
after  hemorrhage,  life  may  be  restored  by  injecting  the  blood, 
defibrinated  or  not,  of  an  animal  of  the  same  species,  pro- 
vided it  be  introduced  slowly,  without  admixture  with  air, 
and  not  in  too  great  quantity.  If,  however,  the  blood  of  an 
animal  of  a  different  species  be  used,  life  will  be  restored  but 
for  a  short  time.  Death  occurs  after  the  transfusion  of  blood 
in  this  instance,  only  when  the  animal  receiving  it  is  exsan- 
guine, and  the  blood  of  an  animal  of  a  different  species  is 
substituted.  If  the  animal  be  not  exsanguine,  a  little  blood 
can  be  superadcled  to  the  mass  from  an  animal  of  different 
species  without  this  result,  as  is  shown  by  the  experiments 

1  BERARD,  op.  tit.,  tome  iii.,  p.  219. 

2  MILNE-EDWARDS,  Lemons  sur  la  Physiologic  el  VAnatomie  Comparee,  tome  i., 
p.  322  et  seq. 

3  Journal  de  la  Physiologic,  tome  i.,  p.  106. 

4  Ibid.,  p.  668. 


100  THE   BLOOD. 

already  alluded  to,  of  transfusion  of  the  blood  of  a  calf  into 
the  veins  of  a  man. 

In  the  human  subject,  especially  after  hemorrhage,  the 
vital  powers  are  sometimes  restored  by  careful  transfusion 
of  human  blood,  with  the  above  precautions;  remembering 
that  a  very  small  quantity,  three  or  four  ounces,  will  some- 
times be  sufficient. 

Quantity  of  Blood. — The  determination  of  the  entire 
quantity  of  blood  contained  in  the  body  is  a  question  of  great 
interest,  and  has  long  engaged  the  attention  of  physiologists, 
without,  however,  absolutely  definite  results.  Among  those 
who  have  experimented  on  this  point,  may  be  mentioned 
Allen-Moulins,  Herbst,  Fried.  Hoffmann,  Yalentin,  Blake, 
Lehmann  and  "Weber,  and  Yierordt.1  The  fact  that  the 
labors  of  these  eminent  observers  have  been  so  far  unsuccess- 
ful in  determining  definitely  the  entire  quantity  of  blood, 
shows  the  difficulties  which  are  to  be  overcome  before  the 
question  can  be  entirely  settled.  The  chief  difficulty  lies  in 
the  fact  that  all  the  blood  is  not  discharged  from  the  body 
on  division  of  the  largest  vessels,  as  after  decapitation ;  and 
no  perfectly  accurate  means  have  been  devised  for  estimating 
the  quantity  which  must  always  remain  in  the  vessels.  The 
estimates  of  experimenters  present  the  following  wide  differ- 
ences. Allen-Moulins,  who  was  one  of  the  first  to  study  this 
question,  estimates  the  quantity  of  blood  at  one-twentieth 
the  weight  of  the  entire  body.  The  estimate  of  Herbst  is  a 
little  higher.  Hoffmann  estimates  the  quantity  at  one-fifth 
the  weight  of  the  body.  These  observers  estimated  the  quan- 
tity remaining  in  the  system  after  opening  the  vessels,  by 
mere  conjecture.  Yalentin  was  the  first  who  attempted  to 
overcome  this  difficulty  by  experiment.  For  this  purpose 

1  The  reader  is  referred  to  the  works  of  Longet  (Physiologic,  Paris,  1861, 
tome  L,  p.  705  et  seg.)  and  Milne-Edwards  (Physiologie,  Paris,  1857,  tome  i.,  p. 
308  et  seq.\  for  a  more  extended  account  of  the  various  experiments  which  have 
been  made  with  a  view  of  determining  the  entire  quantity  of  blood  in  the  body. 


QUANTITY   OF   BLOOD.  101 

he  employed  the  following  process.  He  took  first  a  small 
quantity  of  blood  from  an  animal  for  purposes  of  comparison  ; 
then  injected  into  the  vessels  a  known  quantity  of  a  saline  solu- 
tion, and  taking  another  specimen  of  blood  some  time  after, 
he  ascertained  by  evaporation  the  proportion  of  water  which 
it  contained,  compared  with  the  proportion  in  the  first  speci- 
men. He  reasoned  that  the  excess  of  water  in  the  second 
specimen  over  the  first  would  give  the  proportion  of  the  water 
introduced,  to  the  whole  mass  of  blood;  and  as  the  entire 
quantity  of  water  introduced  is  known,  the  entire  quantity 
of  blood  could  be  deduced  therefrom.  Suppose,  for  example, 
that  the  excess  of  water  in  the  second  specimen  should  be 
one  part  to  ten  of  the  blood,  it  would  show  that  one  part  of 
water  had  been  mixed  with  ten  of  the  blood ;  and  if  we 
had  injected  in  all  five  ounces  of  water,  we  would  have  the 
whole  quantity  of  blood  ten  times  that,  or  fifty  ounces. 

This  method  is  open  to  the  objection  that  it  is  impossi- 
ble to  take  note  of  the  processes  of  imbibition  and  exhalation 
which  are  constantly  in  operation.  Taking  it  for  what  it  is 
worth,  the  estimates,  applied  to  the  human  subject,  give  the 
weight  of  blood  as  -ff^  that  of  the  body. 

Blake  estimated  the  quantity  of  blood  by  an  analogous 
process,  injecting  a  known  quantity  of  sulphate  of  alumina 
into  the  vessels,  estimating  its  proportion  in  a  specimen  of 
blood,  and  from  that  deducing  the  entire  quantity.  He  gives 
the  proportion  of  blood  in  dogs  as  from  one-ninth  to  one- 
third  the  weight  of  the  body.  The  objection  we  have  men- 
tioned applies  also  to  these  experiments. 

The  following  process,  which  is,  perhaps,  least  open  to 
sources  of  error,  was  employed  by  Lehmann  and  Weber,  and 
applied  directly  to  the  human  subject,  in  the  case  of  two 
decapitated  criminals.  These  observers  estimated  the  blood 
remaining  in  the  body  after  decapitation,  by  injecting  the 
vessels  with  water  until  it  came  through  nearly  colorless. 
It  was  carefully  collected,  evaporated  to  dryness,  and  the  dry 
residue  assumed  to  represent  a  certain  quantity  of  blood ;  the 


102  THE   BLOOD. 

proportion  of  dry  residue  to  a  definite  quantity  of  blood 
having  been  previously  ascertained.  If  we  could  be  certain 
that  only  the  solid  matter  of  the  blood  was  thus  removed,  the 
estimate  would  be  tolerably  accurate.  As  it  is,  we  may  con- 
sider it  as  approximating  very  nearly  to  the  truth.  We  quote 
the  following  account  of  these  observations : 

"  My  friend,  Ed.  Weber,  determined,  with  my  coopera- 
tion, the  weights  of  two  criminals  both  before  and  after  their 
decapitation.  The  quantity  of  blood  which  escaped  from  the 
body  was  determined  in  the  following  manner :  Water  was 
injected  into  the  vessels  of  the  trunk  and  head,  until  the  fluid 
escaping  from  the  veins  had  only  a  pale  red  or  yellow  color ; 
the  quantity  of  the  blood  remaining  in  the  body  \vas  then 
calculated,  by  instituting  a  comparison  between  the  solid 
residue  of  this  pale-red  aqueous  fluid,  and  that  of  the  blood 
which  first  escaped.  By  way  of  illustration,  I  subjoin  the 
results  yielded  by  one  of  the  experiments.  The  living  body 
of  one  of  the  criminals  weighed  60,140  grammes  (132*7 
pounds),  and  the  same  body  after  decapitation  54,600  gram- 
mes; consequently  5,540  grammes  of  blood  had  escaped. 
28*560  grammes  of  this  blood  yielded  5*36  grammes  of  solid 
residue ;  60*5  grammes  of  sanguineous  water  collected  after 
the  injection,  contained  3*724  grammes  of  solid  substances ; 
6,050  grammes  of  the  sanguineous 'water  that  returned  from 
the  veins  were  collected,  and  these  contained  37*24  grammes 
of  solid  residue,  which  corresponds  to  1,980  grammes  of 
blood ;  consequently,  the  body  contained  7,520  grammes 
(16*59  pounds),  5,540  escaping  in  the  act  of  decapitation,  and 
1,980  remaining  in  the  body ;  hence,  the  weight  of  the  whole 
blood  was  to  that  of  the  body  nearly  in  the  ratio  of  1:8. 
The  other  experiment  yielded  a  precisely  similar  result. 

"  It  cannot  be  assumed  that  such  experiments  as  these 
possess  extreme  accuracy,  but  they  appear  to  have  the  advan- 
tage of  giving  in  this  manner  the  minimum  of  the  blood  con- 
tained in  the  body  of  an  adult  man ;  for  although  some  solid 
substances,  not  belonging  to  the  blood,  may  be  taken  up  by 


QUANTITY  OF  BLOOD.  103 

the  water  from  the  parenchyma  of  the  organs  permeated  with 
capillary  vessels,  the  excess  thus  obtained  is  so  completely 
counteracted  by  the  deficiency  caused  by  the  retention  of 
some  blood  in  the  capillaries,  and  in  part  by  transudation, 
that  our  estimate  of  the  quantity  of  blood  contained  in  the 
human  body  may  be  considered  as  slightly  below  the  actual 
quantity."  * 

In  extreme  obesity,  the  weight  of  the  blood  would  not 
bear  a  natural  ratio  to  that  of  the  body ;  but  from  the  data 
which  we  have  at  our  command,  we  may  state  the  proportion 
in  a  well-formed  man  to  be  about  1  to  8,  or  the  whole  quantity 
of  blood  at  from  16  to  20  pounds  avoirdupois.  The  quantity 
of  blood  undoubtedly  varies  in  the  same  individual  in  differ- 
ent conditions  of  the  system ;  and  these  variations  are  fully 
as  important,  in  a  physiological  point  of  view,  as  the  entire 
quantity. 

Prolonged  abstinence  has  a  notable  effect  in  diminishing 
the  mass  of  blood,  as  indicated  by  the  small  quantity  which 
can  be  removed  from  the  body,  under  these  circumstances, 
with  impunity.  It  has  been  experimentally  demonstrated2 
that  the  entire  quantity  of  blood  is  considerably  increased 
during  digestion.  Bernard  drew  from  a  rabbit  weighing  about 
2-J-  Ibs.,  during  digestion,  over  10 J-  ounces  of  blood  without 
producing  death ;  .while  he  found  that  the  removal  of  half 
that  quantity  from  an  animal  of  the  same  size,  fasting,  was 
followed  by  death.  In  Burdach,3  we  find  a  case  reported  by 
"Wrisberg,  of  a  female  criminal,  very  plethoric,  from  whom 
21  Ibs.  Tf  ounces  of  blood  flowed  after  decapitation.  As  the 
relations  of  the  quantity  of  blood  to  the  digestive  function 
are  so  important,  it  is  unfortunate  that  in  the  observations 
of  Lehmann  and  Weber,  the  conditions  of  the  system  in  this 

1  LEHMANN,  Physiological  Chemistry,  Philadelphia,  1855,  vol.  i.,  p.  638.     The 
weights  of  the  body  and  the  entire  quantity  of  blood  have  been  reduced  from 
grammes  to  pounds  avoirdupois. 

2  BERNARD,     Liquidcs  de  V  Organisme,   tome  i.,  p.  419. 
8  Op.  tit.,  tome  vi.,  p.  119. 


104:  THE   BLOOD. 

respect  were  not  noted ;  a  circumstance  which  would  have 
added  materially  to  their  value. 

It  is  thus  evident  that  the  quantity  of  blood  in  the  body 
is  considerably  increased  during  digestion ;  but  as  to  the 
extent  of  this  increase,  we  cannot  yet  form  any  definite  idea. 
It  is  only  shown  that  there  is  a  very  marked  difference  in 
the  effects  of  hemorrhage  in"  animals,  during  digestion  and 
fasting. 

The  reaction  of  the  blood,  which  has  been  determined 
after  the  globules  have  separated  so  as  to  allow  the  applica- 
tion of  test  paper  to  the  clear  plasma,  has  been  found  to  be 
uniformly  alkaline. 

Physical  Characters  of  the  Blood. 

Opacity. — One  of  the  first  physical  characters  of  the  blood 
which  attract  our  attention  is  its  opacity.  This  depends 
upon  the  fact  that  it  is  not  a  homogeneous  fluid,  but  com- 
posed of  two  distinct  elements :  a  clear  plasma,  and  corpus- 
cles, which  are  nearly  as  transparent,  but  which  have  a  dif- 
ferent refractive  power.  If  both  of  these  elements  had  the 
same  refractive  power,  the  mixture  would  present  no  obstacle 
to  the  passage  of  light ;  but  as  it  is,  the  rays,  which  are  bent 
or  refracted  in  passing  from  the  air  through  the  plasma,  are 
again  refracted  when  they  enter  the  corpuscles,  and  again 
when  they  pass  from  the  corpuscles  to  the  plasma,  so  that 
they  are  lost,  even  in  a  thin  layer  of  the  fluid.  This  loss  of 
light  in  a  mechanical  mixture  of  two  transparent  liquids  of 
unequal  refractive  power  can  be  demonstrated  by  the  fol- 
lowing simple  experiment.  If  to  a  little  chloroform,  col- 
ored red,  clear  water  be  added  in  a  test-tube,  these  liquids 
remain  distinct  from  each  other,  and  are  both  transparent ; 
but  if  we  agitate  them,  violently,  the  chloroform  is  tempo- 
rarily subdivided  into  globules  and  mixed  with  the  water ; 
and  as  they  refract  light  differently,  the  mixture  is  opaque. 

Odor. — The  blood  has  a  faint  but  characteristic  odor.   This 


PHYSICAL   CHAKACTEBS.  105 

may  be  developed  more  strongly  by  the  addition  of  a  few 
drops  of  sulphuric  acid,  when  an  odor,  peculiar  to  the  animal 
whose  blood  we  are  examining,  becomes  very  distinct. 

Temperature. — The  temperature  of  the  blood  is  generally 
given  as  98°  to  100°  Fahr.,  but  recent  experiments  have 
shown  that  it  varies  considerably  in  different  parts  of  the 
circulatory  system,  independently  of  exposure  to  the  refrig- 
erating influence  of  the  atmosphere.  By  the  use  of  very 
delicate  registering  thermometers,  Bernard  has  succeeded  in 
establishing  the  following  facts  with  regard  to  the  temperature 
in  various  parts  of  the  circulatory  system  in  dogs  and  sheep : 

1.  The  blood  is  warmer  in  the  right  than  in  the  left  cav- 
ities of  the  heart. 

2.  It  is  warmer  in  the  arteries  than  in  the  veins,  with  a 
few  exceptions. 

3.  It  is  generally  warmer  in  the  portal  vein  than  in  the 
abdominal  aorta,  independently  of  the  digestive  act. 

4.  It  is  constantly  warmer  in  the  hepatic  than  in  the 
portal  veins. 

He  found  the  highest  temperature  in  the  blood  of  the 
hepatic  vein,  where  it  ranged  from  101°  to  107°.  In  the 
aorta  it  ranged  from  99°  to  105°. 

We  may  assume,  then,  in  general  terms,  that  the  tem- 
perature of  the  blood  in  the  deeper  vessels  is  from  100°  to 
107°  Fahrenheit.1 

Specific  Gravity  of  the  Blood. — According  to  Becquerel 
and  Eodier,  who,  perhaps,  are  as  high  authority  as  any  on 
this  subject,  the  specific  gravity  of  defibrinated  blood  is  from 
1055  to  1063.2  It  is  somewhat  less  in  the  female  than  in 
the  male. 

1  These  facts  were  taken  from  the  lectures  of  Bernard,  "  Sur  les  Liquides  de 
V  Organisme,"  Paris,  1859,  in  two  volumes.     The  first  volume  is  devoted  to  th<J 
blood,  and  the  subject  of  temperature  is  very  thoroughly  investigated. 

2  BECQUEREL  aud  RODIER,     Traite  de  Chimie  Pathologique,    Paris,  1854. 


106  THE   BLOOD. 

Color  of  the  Blood. — The  color  of  the  blood  is  due  to  the 
corpuscles.  In  the  arterial  system  it  is  uniformly  red.  In 
the  veins  it  is  dark  blue  and  sometimes  almost  black.  This 
difference  in  color  between  the  blood  in  the  arterial  and  in 
the  venous  system,  was  a  matter  of  controversy  at  the  time 

of  Harvey.     By  the  discoverer  of  the  circulation,  the  differ- 

•j          «/  « 

ence,  which  is  now  universally  known  and  admitted,  as  re- 
gards most  of  the  veins,  was  supposed  to  be  merely  accidental, 
and  dependent  on  external  causes.  Fifty  years  later,  Lower1 
demonstrated  the  change  of  color  in  the  blood  as  it  passes 
through  the  lungs,  and  associated  it  with  the  true  cause,  vis., 
the  absorption  of  oxygen.  The  color  in  the  veins,  however, 
is  not  constant.  Many  years  ago,  John  Hunter  observed,  in 
a  case  of  syncope,  that  the  blood  drawn  by  venesection  was 
bright  red ; 2  and  more  recently  Bernard  has  demonstrated 
that  in  some  veins  the  blood  is  nearly,  if  not  quite,  as  red  as 
in  the  arterial  system.  The  color  of  the  venous  blood  de- 
pends upon  the  condition  of  the  organ  or  part  from  which  it 
is  returned.  The  red  color  was  first  noticed  by  Bernard  in 
the  renal  veins,  where  it  contrasts  very  strongly  with  the 
black  blood  in  the  vena  cava.  He  afterwards  observed  that 
the  redness  only  existed  during  the  functional  activity  of  the 
kidneys ;  and  when,  from  any  cause,  the  secretion  of  urine 
was  arrested,  the  blood  became  dark.  He  was  led  from  this 
observation  to  examine  the  venous  blood  from  other  glands ; 
and  directing  his  attention  to  those  which  he  was  able  to 
examine  during  their  functional  activity,  particularly  the 
salivary  glands,  found  the  blood  red  in  the  veins  during 
secretion,  but  becoming  dark  as  soon  as  secretion  was  arrested. 
These  observations  may  be  easily  verified  by  opening  the 
abdomen  of  a  living  animal  so  as  to  expose  the  emulgent 
veins,  introducing  a  canula  into  the  ureter  so  as  to  be  able 
to  note  the  flow  or  arrest  of  the  urine.  •  As  long  as  the  urine 

1  LOWER,  Tractatus  de  Corde  item  de  Motu  &  Oolore  Sanguinis,  Amstelodami, 
1669,  p.  180. 

a  The  Works  of  John  Hunter,  Philadelphia,  1840,  vol.  iii.,  p.  93. 


PHYSICAL   CHAEACTEES.  107 

continues  to  flow,  the  blood  in  these  vessels  will  be  bright 
red ;  but  when  secretion  becomes  arrested,  as  it  soon  does 
after  exposure  of  the  organs,  it  presents  no  difference  from 
the  blood  in  the  vena  cava.  In  the  sub-maxillary  gland,  by 
the  galvanization  of  a  certain  nerve,  which  he  calls  the  motor- 
nerve  of  the  gland,  Bernard  has  been  able  to  produce  secre- 
tion, and  by  the  galvanization  of  another  nerve,  to  arrest  it ; 
in  this  way  changing  at  will  the  color  of .  the  blood  in  the 
vein.  It  has  been  found  by  the  same  observer  that  division 
of  the  sympathetic  in  the  neck,  which  dilates  the  vessels  and 
increases  the  supply  of  blood  to  one  side  of  the  head,  produces 
a  red  color  of  the  blood  in  the  jugular.  He  has  also  found 
that  paralysis  of  a  member  by  division  of  the  nerve  has  the 
same  effect  on  the  blood  returning  by  the  veins. ' 

The  explanation  of  these  facts  is  evident  when  we  reflect 
upon  the  "reasons  why  the  blood  is  red  in  the  arteries  and 
dark  in  the  veins.  Its  color  depends  upon  the  corpuscles ; 
and  as  the  blood  passes  through  the  lungs  it  loses  carbonic 
acid  and  gains  oxygen,  changing  from  black  to  red.  In  its 
passage  through  the  capillaries  of  the  system,  in  the  ordinary 
processes  of  nutrition,  it  loses  oxygen  and  gains  carbonic  acid, 
changing  from  red  to  black.  During  the  intervals  of  secre- 
tion, the  glands%have  just  enough  blood  sent  to  them  for  their 
nutrition,  and  the  ordinary  interchange  of  gases  takes  place, 
with  the  consequent  change  of  color ;  but  during  their  func- 
tional activity,  the  blood  is  supplied  in  greatly  increased 
quantity,  in  order  to  furnish  the  watery  elements  of  the 
secretions.  Under  these  circumstances  it  does  not  lose 
oxygen  and  gain  carbonic  acid  in  any  great  quantity,  as  has 
been  demonstrated  by  actual  analysis,2  and  consequently 
experiences  no  change  in  color.  "When  filaments  of  the  sym- 
pathetic are  divided,  the  vessels  going  to  the  part  are  dilated, 
and  the  supply  of  blood  is  increased  to  such  an  extent,  that  a 

1  BERNARD,  op.  cii. 

2  Unpublished  lectures  delivered  by  Bernard  in  the  College  of  France  during 
the  summer  of  1861. 


108 


THE   BLOOD. 


certain  proportion  passes  through  without  parting  with  its 
oxygen,  a  fact  which  has  also  been  demonstrated  by  analysis, 
and  consequently  retains  its  red  color.  The  explanation  in 
cases  of  syncope  is  probably  the  same ;  though  this  is  merely 
a  supposition.  Even  during  secretion,  a  certain  quantity  of 
carbonic  acid  is  formed  in  the  gland,  which,  according  to 
Bernard,  is  carried  off  in  solution  in  the  secreted  fluid.1 

It  may  be  stated  in  general  terms  that  the  color  of  the 
blood  in  the  arteries  is  bright  red ;  and  in  the  ordinary  veins, 
like  the  cutaneous  or  muscular,  it  is  dark  blue,  almost  black. 
It  is  red  in  the  veins  coming  from  glands  during  secretion,  and 
dark  during  the  intervals  of  secretion. 

Anatomical  Elements  of  the  Blood. 

In  1661,  the  celebrated  anatomist,  Malpighi,  in  examining 
the  blood  of  the  hedgehog  with  the  feeble  and  imperfect 
lenses  at  his  command,  discovered  little  floating  particles 
which  he  mistook  for  granules  of  fat,  but  which  were  the 
blood-corpuscles.  He  did  not  extend  his  observations  in 
this  direction;  but  a  few  years  later  (1673),  Leeuwen- 
hoek,  by  the  aid  of  simple  lenses  of  his  own  construction, 
varying  in  magnifying  power  from  40  to  160  diameters,  first 
saw  the  corpuscles  of  human  blood,  which  he  minutely 
described  in  a  paper  published  in  the  Philosophical  Trans- 
actions, in  1674.  To  him  is  generally  ascribed  the  honor  of 
the  discovery  of  the  blood-corpuscles.  About  a  century  later, 
William  Hewson2  described  another  kind  of  corpuscles  in 
the  blood,  which  are  much  less  abundant  than  the  red,  and 
which  are  now  known  under  the  name  of  white  globules,  or 
as  they  have  lately  been  called  by  Robin,  leucocytes. 

Without  following  the  progress  of  microscopic  investiga- 

1  BERNARD,  op.  cit.,  tome  i.,  p.  346. 

2  The  Works  of  William  Hewson,  F.  R.  S.,  Sydenham  Society  edition,  London, 
1846. 


ANATOMICAL    ELEMENTS.  109 

tions  into  the  constitution  of  the  blood,  it  may  be  stated 
that  it  is  now  known  to  be  composed  of  a  clear  fluid,  the 
Plasma,  or  liquor  sanguinis,  holding  certain  corpuscles  in 
suspension.  These  corpuscles  are 

1.  Red  Corpuscles;  by  far  the  most  abundant,  constituting 
about  one-half  of  the  mass  of  blood. 

2.  Leucocytes,  or  White  Corpuscles  ;  much  less  abundant, 
existing  only  in  the  proportion  of  one  to  several  hundred  red 
corpuscles. 

3.  Granules  /    exceedingly    minute,    called,    by   Milne- 
Edwards,  globulins,  and  by  Kolliker,  elementary  granules. 
These  are  few  in  number,  and  are  undoubtedly  fatty  particles 
from  the  chyle.     They  are  to  be  regarded  as  accidental  con- 
stituents of  the  blood. 

Red  Corpuscles. — These  little  bodies  give  to  the  blood  its 
red  color  and  its  opacity.  They  are  true  organized  structures, 
containing  organic-nitrogenized  and  inorganic  elements  molec- 
ularly  united,  and,  as  an  exception  to  the  general  rule,  a  lit- 
tle fatty  matter  in  union  with  their  organic  principle.  Like 
other  organized  structures,  they  are  constantly  undergoing 
decay,  and  are  capable  of  self-regeneration.  They  constitute 
about  one-half  the  mass  of  blood,  and,  according  to  the  obser- 
vations of  all  who  have  investigated  this  subject,  are  more 
abundant  in  the  male  than  in  the  female ;  this  constituting, 
perhaps,  the  only  constant  difference  in  the  composition  of 
the  blood  in  the  sexes. 

The  form  of  the  blood-corpuscles  is  peculiar.  They  are 
flattened,  bi-concave,  circular  disks,  with  a  thickness  of  from 
one-fourth  to  one-third  of  their  diameter.  Their  edges  are 
rounded,  and  the  thin  central  portion  occupies  about  one-half 
of  their  diameter.  Their  consistence  is  not  much  greater 
than  that  of  the  plasma.  They  are  very  elastic,  and  if  de- 
formed by  pressure,  immediately  resume  their  original  shape 
when  the  pressure  is  removed.  Their  specific  gravity  is  some- 
what greater  than  that  of  the  plasma. 


110  THE   BLOOD. 

The  peculiar  form  of  the  blood-corpuscles  gives  them  a 
very  characteristic  appearance  under  the  microscope.  "When 
examined  with  a  magnifying  power  of  from  300  to  500 
diameters,  those  which  present  their  flat  surfaces  have  a 
shaded  centre,  when  the  edges  are  in  focus.  Before  we  were 
in  possession  of  the  perfect  instruments  now  used  in  micro- 
scopic investigation,  this  spot  was  supposed  to  be  a  nucleus 
having  a  constitution  different  from  the  rest  of  the  corpuscle. 
Now  this  is  understood  to  be  an  optical  effect,  the  result  of 
the  form  of  the  corpuscle;  their  bi-concavity  rendering  it  im- 
possible for  the  centre  and  edges  to  be  exactly  in  focus  at 
the  same  instant,  so  that  when  the  edges  are  in  focus  the 
centre  is  dark,  and  when  the  centre  is  bright  the  edges  are 
shaded. 

As  the  blood-corpuscles  are  examined  by  the  microscope 
by  transmitted  light,  they  are  quite  transparent,  and  of  a 
pale  amber  color.  It  is  only  when  they  are  collected  in 
masses  that  they  present  the  red  tint  characteristic  of  blood 
as  it  appears  to  the  naked  eye.  This  yellow  or  amber  tint  is 
characteristic.  A  pretty  good  idea  of  it  may  be  obtained  by 
largely  diluting  blood  in  a  test  tube  and  holding  it  between 
the  eye  and  the  light. 

In  examining  blood  under  the  microscope,  the  corpuscles 
are  seen  in  many  different  positions ;  some  flat,  some  on  their 
edges,  etc.  This  assists  us  in  recognizing  their  peculiar 
form. 

It  has  been  observed  by  microscopists  that  the  blood- 
corpuscles  have  a  remarkable  tendency  to  arrange  themselves 
in  rows  like  rouleaux  of  coin.  This  has  attracted  universal 
attention,  and  for  a  long  time  was  not  satisfactorily  explained. 
Robin  has  lately  given  us  what  seems  to  be  the  true  explana- 
tion of  this  phenomenon.1  This  observer  has  shown  that 


1  ROBIN,  Sur  quelques  Points  de  VAnatomie  et  de  la  Physiologic  dcs  Globulea 
Rouges  du  Sang. — Journal  de  la  Physiologic  de  VHomme  et  des  Animaux, 
Paris,  1858,  tome  L,  p.  295. 


BED   CORPUSCLES.  Ill 

shortly  after  removal  from  the  vessels,  there  exudes  from  the 
corpuscles  an  adhesive  substance  which  smears  their  surface 
and  causes  them  to  stick  together.  Of  course  the  tendency 
is  to  adhere  by  their  flat  surfaces.  In  examining  a  specimen 
of  blood  under  the  microscope,  the  presence  of  this  adhesive 
exudation  may  be  demonstrated  by  employing  firm  and 
gradual  pressure  on  the  glass  cover,  when  the  adherent  cor- 
puscles may  be  separated  in  some  instances,  and  with  oblique 
light  we  can  sometimes  see  a  little  transparent  filament  be- 
tween them,  which  draws  them  together,  as  it  were,  when 
the  pressure  is  removed.  This  phenomenon  is  due  to  a  post 
mortem  change,  but  it  occurs  so  soon,  that  it  presents  itself  in 
nearly  every  specimen  of  fresh  blood  which  we  examine,  and 
is  therefore  mentioned  in  connection  with  the  normal  charac- 
ters of  the  blood-corpuscles. 

Dimensions. — The  diameter  of  the  blood-corpuscles  has  a 
more  than  ordinary  anatomical  interest ;  for,  varying  perhaps 
less  in  size  than  in  other  anatomical  elements,  they  are  rather 
taken  as  the  standard  by  w^hich  we  form  an  idea  of  the  size 
of  other  microscopic  objects.  The  diameter  usually  given  is 
^jVo-  °f  an  inch.  The  exact  measurement  given  by  Robin  is 
.0073  of  a  millimetre 1  .or  ^^T  of  an  inch.  It  is  stated  by 
some  authors  that  the  size  of  the  corpuscles  is  very  variable, 
even  in  a  single  specimen  of  blood.  I  have  repeatedly 
measured  them  with  the  eye-piece  micrometer  of  Cachet, 
and  found  a  diameter  of  -g^Vo-  of  an  inch.  Yery  few  are  to 
be  found  which  vary  from  this  measurement.  Kolliker,  who 
gives  their  average  diameter  as  -g^Vo-  of  an  inch,  states  that 
"  at  least  ninety-five  out  of  every  hundred  corpuscles  are  of 
the  same  size." 2 

"We  cannot  leave  the  subject  of  the  size  of  the  blood-cor- 
puscles without  a  notice  of  the  measurements  in  the  blood  of 


1  Loc.  at. 

*  KOLLIKER,  Manual  of  Microscopic  Anatomy,  London,  1860,  p.  619, 


112  THE   BLOOD. 

different  animals.  This  point  is  interesting  from  the  fact 
that  it  is  often  an  important  question  to  determine  whether  a 
given  specimen  of  blood  be  from  the  human  subject  or  one 
of  the  inferior  animals.  Comparative  measurements  also 
have  an  interest  on  account  of  a  relation  which  seems  to 
exist  in  the  animal  scale  between  the  size  of  the  blood-cor- 
puscles, and  muscular  activity.  In  all  the  mammalia,  with 
the  exception  of  the  camel  and  lama,  in  which  they  are  oval, 
the  blood-corpuscles  have  the  same  anatomical  characters  as 
in  the  human  subject ;  the  only  difference  is  in  size.  In  only 
two  animals,  the  elephant  and  sloth,  are  they  larger  than  in 
?nan ;  in  all  others  they  are  smaller,  or  of  nearly  the  same 
diameter.  By  reference  to  the  table  it  will  be  seen  that  in 
some  animals  the  corpuscles  are  very  much  smaller  than  in 
man ;  and  by  accurate  measurement,  we  are  enabled  to  dis- 
tinguish their  blood  from  the  blood  of  the  human  subject. 
But  in  forming  an  opinion  on  this  subject,  it  must  be  remem- 
bered that  there  is  some  variation  in  the  size  of  the  corpuscles 
of  the  same  animal.  We  can  easily  distinguish  the  blood  of 
the  human  subject,  or  of  the  mammals  generally,  from  that 
of  birds,  fishes,  or  reptiles ;  for  in  these  classes  of  animals  the 
corpuscles  are  oval  and  contain  a  granular  nucleus. 

Milne-Edwards  has  attempted  to  show,  by  a  comparison 
of  the  diameter  of  the  blood-corpuscles  in  different  species, 
that  their  dimensions  are  in  inverse  ratio  to  the  muscular 
activity  of  the  animal.1  Reference  to  the  table  will  show 
that  this  relation  holds  good  to  a  certain  extent,  while  there 
certainly  exists  none  between  the  size  of  the  corpuscle  and 
the  size  of  the  animal.  In  deer,  which  are  remarkable  for 
their  muscular  activity,  the  corpuscles  are  very  small,  5  oV^ 
of  an  inch ;  while  in  the  sloth  they  are  ^sV o-,  and  in  the  ape, 
which  is  comparatively  inactive,  ^Vo-  But,  on  the  other 
hand,  in  the  dog,  which  is  quite  active,  we  have  a  corpuscle 


1  MILNE-EDWARDS,    Legons  sur  la  Physiologic   et  PAnatomie    Comparee, 
tome  i.,  p.  57  et  seg. 


BED  COKPUSCLES.  113 

of  -3  jV  o-  °f  an  inch,  and  in  the  ox,  which  is  certainly  not  so 
active,  the  diameter  of  the  corpuscle  is  J^TT  of  an  incn- 
Though  this  relation  between  the  size  of  the  blood-corpuscles 
and  muscular  activity  is  not  invariable,  it  is  certain  that  the 
higher  we  go  in  the  great  classes  of  animals,  the  smaller  the 
blood-corpuscle  becomes ;  the  largest  being  found  in  the  lowest 
orders  of  reptiles,  and  the  smallest  in  the  mammalia.  In  the 
blood  of  the  invertebrates,  with  a  few  exceptions,1  we  find  no 
colored  corpuscles. 

Table  of  Measurements  of  Red  Corpuscles. 

This  table  is  taken  from  the  table  of  Mr.  Gulliver,  published  in  the  Sydenham 
edition  of  Hewson's  Works,  page  237.  Nearly  five  hundred  measurement  were 
made  by  Mr.  Gulliver ;  and  of  these,  one  hundred  of  the  most  important  have  been 
selected.  It  will  be  observed  that  the  diameter  of  the  human  blood-corpuscle  is 
greater  than  that  generally  given.  It  must  be  borne  in  mind  that  all  these  meas- 
urements are  mere  approximations ;  but  as  such  they  are  useful,  as  showing  the 
relations  of  the  corpuscles  in  different  animals,  and  enabling  us  to  distinguish 
the  blood  of  the  human  subject  from  that  of  some  of  the  inferior  animals ; 
a  question  which  is  often  of  vital  importance.  The  measurements  are  all  given 
in  fractions  of  an  English  inch ;  and  in  making  the  selections,  the  common  names 
of  the  animals  have  been  substituted  for  the  technical  names  given  in  the  original. 


Diameter. 


MAMMALS. 

Corpuscles  Circular. 

Diameter.                                                        D 
,  ,1  n     "Whale 

Chimpanzee,   . 
Ourang-Outang, 
Black  Monkey, 
Bed  Monkey, 
Cape  Baboon, 

•    infra-    Hog,          . 
WST    Indian  Elephant,    . 
•     guVo     Indian  Ehinoceros,    . 
ir/97    Horse,    .... 

Brown  Baboon, 
Dog-faced  Baboon, 
Lazy  Monkey,     . 

.        .        TrtVir    Stag,      .... 
•    mnrr    Fallow  Deer,     . 
TeVx    Virginia  Deer, 

4  6  0  0 
4T5T5 


1  Note  sur  V Existence  de  Globules  de  Sang  colores  chez  plusieurs  d'animanx  in- 
vcrtebres.  Par  le  Docteur  CH.  ROUGET.  Journal  de  la  Physiologic,  &c.,  Paris, 
1859,  tome  ii.,  p.  660.  In  this  article  Dr.  Rouget  cites  a  number  of  invertebrate 
animals,  in  the  blood  of  which  he  has  found  corpuscular  elements.  This  is  op 
posed  to  the  general  idea  that  corpuscles  exist  only  in  the  blood  of  the  verte- 
brates. 

8 


114 


THE    BLOOD. 


Diameter. 


Diameter. 


Bat, nVr  Giraffe,      . 

Long-eared  Bat,          .        .  ^5-  Antelope, 

Mole, ffof  Gazelle,     ....  ?-^- 

Hedgehog,          .        .        .  ^3-  Goat,     ....  -^Vg- 

Badger,          ....  -yfav  Sheep, 

Polar  Bear,         .        .        .  ^w  Ox,        ... 

Brown  Bear  of  Europe,          .  ^VF  Buffalo,     ....  ffo-s 

Black  Bear  of  K  America,  -3-5^-  Musk  Deer  of  Java,        .  TS&TX 

Eacoon,          ....  ^-gVo-  Flying  Squirrel,         .        .  -5-^- 

Dog,   .        .        .        .        .  -s^  Eed  Squirrel,         .        .  ToVo- 

Fox, ^TVr  Black  Squirrel,          .        .  -5-5^ 

Jackal,        ....  mmr  Gray  Squirrel,        .        .  ^^ 

Wolf, -jrsVo-  Marmot,    . 

Striped  Hyena,    .        .        .  ^Vr  Brown  Eat,   . 

Spotted  Hyena,      .        .        .  -g-gVir  Black  Eat, 

Cat, •jiVi"  Mouse,  ....  -g-fay 

Lion, yfay  Water  Eat,        .        .        .  -jTVir 

Tiger,          ....  j^rr  Porcupine,     .        .        .  ^^r 

Leopard,        ....  ^o-  Beaver,     ....  -5-^ 

Panther,     ....  ^Vs-  Guinea  Pig,   .        .        .  -g^V* 

Ferret, 4-T5T  Rabbit,      .                 .        .  ^Vr 

Weasel,       .        .        .        .  4^0-5-  Two-toed  Sloth,     .        .  ^^ 

Polecat,          .        .        .        .  4-rVr  Opossum,           .        .        .  ^y 

Otter,          ....  -g^Vs*  Kangaroo,      .        .        .  -g^V? 

L.  diam.  S.  diam. 

Seal, -g^Vr  Dromedary  (oval),       -g^Vr  Wn 

Porpoise,    ....  ?fa  Camel          (oval), 


BIRDS. 


Corpuscles  Oval. 


Long        Short 
Diameter.  Diameter. 


Eagle  (ring-tailed), 

Owl, 

Jay, 

Eaven,     . 

Starling, 

Wren, 

Sparrow, 

Woodpecker,    . 

Swallow, 

Stork,       . 


3-rVr 


TTTT 
•2-T5T 

irA-ir 


Pigeon, 

Turtle-dove, 

Peacock, 

Cock,      . 

Turkey, 

Guinea-fowl, 

Quail, 

Goose,    . 

Swan, 


Long      Short 
Diam'r.  Diam'r. 


'2  oo  5"  STST 
1835"  ^589 
2102' 


Tijnr 

'18  Off      ttTZ 
TT3T      1T2~? 


BED   CORPUSCLES.  115 

REPTILES. 

Corpuscles  Oval. 

Long     Short  Long       Short 

Diam'r.  Diam'r.  •  Diam'r.  Diam'r. 

Green  turtle,        .        .    -j-^i     rswz    Lizard, 
Land  tortoise,  .        -^^    TZTS    Viper,     . 


AMPHIBIA. 

Corpuscles  Oval. 

Long      Short  Long       Short 

Diam'r.  Diam'r.  Diam'r.  Diam'r. 

Toad  .        . 


FISHES. 

Corpuscles  Oval. 

«  Long      Short  Long       Short 

Diam'r.  Diam'r.  Diam'r.  'Diam'r. 

Perch,      .        .        .        TnjViF    2-gVr    Pike>       •        •        •    innnr 
Carp,  .        .        .    1nVr    ^Vir    Eel.     .        .        . 


Post-mortem  Changes  of  Blood-Corpuscles.  —  In  examining 
the  fresh  blood  under  the  microscope,  after  the  specimen  has 
been  under  observation  a  short  time,  the  corpuscles  assume  a 
peculiar  appearance,  from  the  development  on  their  surface 
of  very  minute  rounded  projections,  like  the  granules  of  a 
raspberry;  indeed  they  are  said  by  the  French  to  become 
framboisees,  which  expresses  the  appearance  very  well.  A 
little  later,  when  they  have  become  desiccated  to  a  certain 
extent,  they  .present  a  shrunken  appearance,  and  their  edges 
become  serrated.  Under  these  circumstances,  their  original 
form  may  be  restored  by  adding  to  the  specimen  a  liquid  of 
the  density  of  the  serum.  "When  they  have  been  completely 
dried,  as  in  blood  spilled  upon  clothing  or  a  floor,  months 
or  even  years  after,  they  can  be  made  to  assume  their  char- 
acteristic form  by  being  carefully  moistened  with  an  appro- 
priate fluid.  This  property  is  taken  advantage  of  in  exami- 
nations of  old  spots  supposed  to  be  blood  ;  and  if  the  manipu- 


116  THE   BLOOD. 

lations  be  carefully  conducted,  the  corpuscles  may  be  recog- 
nized without  difficulty  by  the  microscope.1 

If  pure  water  be  added  to  a  specimen  of  blood  under  the 
microscope,  the  corpuscles  will  first  swell  up,  become  spher- 
ical, and  are  finally  lost  to  view  by  solution.  The  same  effect 
follows  almost  instantaneously  on  the  addition  of  acetic  acid. 

Structure. — The  structure  of  the  blood-corpuscles  is  very 
simple.  They  are  perfectly  homogeneous,  presenting,  in 
their  normal  condition,  no  nuclei  nor  granules,  and  are  not 
provided  with  an  investing  membrane.  A  great  deal  has 
been  said  by  anatomists  concerning  this  latter  point,  and 
many  are  of  the  opinion  that  they  are  cellular  in  their  struc- 
ture, being  composed  of  a  membrane,  with  viscid,  semi-fluid 
contents.  Without  going  fully  into  the  discussion  of  this 
point,  it  may  be  stated  that  few  have  assumed  actually  to 
demonstrate  this  membrane;  but  they  hate,  for  the  most 
part,  inferred  its  existence  from  the  fact  of  the  swelling,  and 
as  they  term  it,  bursting  on  the  addition  of  water ;  and  par- 
ticularly, as  it  seems  to  me,  to  make  the  blood-corpuscles 
obey  the  theoretical  laws  of  cell-development  and  nutrition 
laid  down  by  Schwann.  Their  great  elasticity,  the  persist- 
ence with  which  they  preserve  their  bi-concave  form,  and 
their  general  appearance,  would  rather  favor  the  idea  that 
they  are  homogeneous  bodies  of  a  definite  shape,  than  that 
they  have  a  cell-wall  with  semi-fluid  contents ;  especially  as 
the  existence  of  a  membrane  has  been  interred  rather  than 
demonstrated.  Their  mode  of  nutrition  is  like  that  of  any 
other  anatomical  elements.  They  are  continually  bathed  in 
a  nutritive  fluid,  the  plasma,  and  as  fast  as  their  substance 
becomes  worn  out  and  effete,  new  material  is  supplied.  In 
this  way  they  undergo  the  same  changes  as  other  anatomical 
elements.  When  destroyed,  or  removed  from  the  body  in 

1  For  full  directions  for  the  examination  of  blood  stains,  the  reader  is  referred 
to  an  article  on  the  medico-legal  examination  of  spots  of  blood  by  Robin,  in  the 
Buffalo  Medical  Journal,  1857-'58.  Vol.  xiii.,  p.  555 


BED  COEPUSCLES.  117 

hemorrhages,  new  corpuscles  are  gradually  developed,  until 
their  quantity  reaches  the  normal  standard.  Thus  in  the 
anemia  which  follows  considerable  loss  of  blood,  the  color 
gradually  returns  with  the  development  of  the  corpuscles. 

Chemical  Characters. — In  all  chemical  analyses  of  the 
blood-corpuscles,  the  proportions  of  dried  constituents  only 
are  given.  As  we  have  seen  in  treating  of  organic-nitrogen- 
ized  elements,  such  estimates  give  no  idea  of  the  actual  pro- 
portions of  the  organic  constituents  of  fluids  or  tissues.  We 
must  consider  the  corpuscles  as  organized  bodies,  consisting 
almost  entirely  of  globuline,  with  which  are  combined  a 
small  quantity  of  hsematine,  or  coloring  matter,  fat,  and  cer- 
tain inorganic  salts,  from  which  it  cannot  be  separated  with- 
out decomposition.  The  chemical  characters  of  globuline 
have  already  been  considered.1  The  iron  which  the  blood 
contains  is  regarded  as  existing  in  the  hsematine.  Its  pres- 
ence can  readily  be  demonstrated  in  a  single  drop  of  blood 
by  adding  nitric  acid  and  evaporating,  which  reduces  it  to 
the  condition  of  a  per-oxide,  when  a  red  color  is  produced  on 
the  addition  of  the  sulpho-cyanide  of  potassium.  The  iron 
is  molecularly  united  with  the  other  constituents,  probably 
as  iron,  and  not  as  an  oxide,  as  has  been  supposed  by  some.2 
The  fat  which  is  found  in  the  corpuscles  forms  an  exception 
to  the  general  law  regulating  the  condition  of  this  principle 
in  the  tissues,  namely,  that  it  is  always  uncombined  with 

1  Vide  page  90. 

2  Crystals  have  long  been  observed  in  blood  under  certain  circumstances. 
Sir  Everhard  Home  first  observed  them  in  the  clots  of  aneurismal  sacs  in  1830. 
Since  then  they  have  been  described  by  Scherer,  Virchow,  and  others,  and  by 
many  are  supposed  to  be  pure  hsematine,  or  the  normal  coloring  matter  of  the  red 
corpuscles.     Robin  and  Yerdeil,  who  have  studied  them  very  closely,  do  not  con- 
sider these  crystals  as  constituting  a  proximate  principle,  but  as  formed  by  an 
alteration  of  the  hsematine,  consisting  in  the  substitution  of  water  for  the  iron. 
By  careful  analysis,  these  observers  have  failed  to  detect  any  iron  entering  into 
their  composition.     They  are  treated  of  in  their  "  Chimie  Anatomique,"  under 
Hcernatoidine.     Op.  tit.,  tome  iii.,  pp.  376  and  430,    and  Kysterfs  Dictionary, 
1858.     Hcemato'idine. 


118 


THE   BLOOD. 


other  principles,  existing  as  adipose  tissue  or  in  granules. 
Here  it  is  molecularly  united  with  the  other  elements. 

In  accordance  with  the  invariable  law,  that  the  organic 
nitrogenized  elements  of  the  body  are  combined  with  inor- 
ganic principles,  we  find  entering  into  the  composition  of  the 
blood-corpuscles  certain  inorganic  salts.  These  all  exist  in 
the  plasma  in  about  the  same  proportions  as  in  the  cor- 
puscles. In  short,  as  we  shall  see  when  we  take  up  the  com- 
position of  the  entire  blood,  the  corpuscles  differ  from  the 
plasma  only  in  the  fact  that  they  contain  coloring  matter  and 
globuline,  instead  of  fibrin  and  albumen,  and  that  the  fat  is 
united  with  the  organic  matter  instead  of  being  in  distinct 
granules.  In  all  other  respects  their  composition  is  nearly 
identical.  "We  can  thus  appreciate  how  favorable  their  con- 
stitution and  situation  are  for  their  nutrition  at  the  expense 
of  elements  furnished  by  the  plasma.1 

Development  of  the  Blood-Corpuscles.— Yery  early  in  the 
development  of  the  ovum  the  blood-vessels  appear,  consti- 

1  Lehmann  gives  the  following  table  showing  the  comparative  composition  of 
the  corpuscles  and  plasma ;  the  organic  matters  being  desiccated. 
1000  parts  of  Blood-Corpuscles 


contain : 

Water, 

Solid  constituents, 312-00 

Specific  Gravity,  1.0885. 

Hematine, 16-75 

Globuline  and  cell-membrane, 282-22 

Fat, 2-31 

Extractive  matters, 2-60 

Mineral  substances  (without  iron), 812 


Chlorine, 1-680 

Sulphuric  Acid 0-066 

Phosphoric  Acid, 1'134 

Potassium,  3-328 

Sodium, 1-052 

Oxygen, 0-667 

Phosphate  of  Lime, 0-114 

Phosphate  of  Magnesia, 0-073 


1000  parts  of  Liquor  Sanguinis 
contain : 

Water, 902-90 

Solid  constituents, 97-10 


Specific  gravity,    1-028 


Fibrin, 4-05 

Albumen, 7S-84 

Fat, 1-72 

Extractive  matters, 3'94 

Mineral  substances, 8-55 


Chlorine, 3'664 

Sulphuric  Acid, 0-115 

Phosphoric  Acid, 0-191 


Potassium,  » . 
Sodium, 


0-323 


Oxygen, 0403 

Phosphate  of  Lime, 0-311 

Phosphate  of  Magnesia, 0-222 


— Physiological  Chemistry.     Philadelphia,  1855 ;  vol.  i.,  p.  546. 


RED   CORPUSCLES.  119 

tuting  what  is  called  the  area  yasculosa.  At  first  the  vessels 
are  filled  with  a  colorless  fluid,  which  soon  becomes  yellow, 
and  when  the  embryo  is  about  one-tenth  of  an  inch  in  length, 
becomes  red,  and  the  corpuscles  make  their  appearance.  From 
this  time  until  the  sixth  to  the  eighth  week,  they  are  from 
30  to  100  per  cent,  larger  than  in  the  adult.  Most  of  them 
are  circular,  but  some  are  ovoid,  and  a  few  are  globular.  At 
this  period,  nearly  all  of  them  are  provided  with  a  nucleus  ; 
but  from  the  first,  there  are  some  in  which  this  is  wanting. 
The  nucleus  is  from  TTijnr  to  -g^Vo  of  an  inch  in  diameter, 
globular,  granular,  and  insoluble  in  water  and  acetic  acid. 
As  development  advances,  these  nucleated  corpuscles  are 
gradually  lost ;  but  even  at  the  fourth  month  we  may  still 
see  a  few  remaining.  After  this  time  they  present  no  ana- 
tomical differences  from  the  blood-corpuscles  in  the  adult. 

In  many  works  on  physiology  and  microscopic  anatomy, 
we  find  accounts  of  the  development  of  the  red  corpuscles 
from  the  colorless  corpuscles^  or  leucocytes,  which  are  sup- 
posed to  become  disintegrated,  their  particles  becoming  de- 
veloped into  red  corpuscles ;  but  there  seems  to  be  no  suffi- 
cient evidence  that  such  a  process  takes  place.  The  red 
corpuscles  appear  before  the  leucocytes  are  formed ; 1  and  it 
is  only  the  fact  that  the  two  varieties  coexist  in  the  blood- 
vessels which  has  given  rise  to  such  a  theory.'  It  is  most 
reasonable  to  consider  that  the  red  corpuscles  are  formed  by 
a  true  genesis  in  the  sanguineous  blastema.  We  can  offer 
no  satisfactory  explanation  of  the  process  by  which  the  tissues 
are  formed  from  their  blastema,  nor  can  we  explain  the  way 
in  which  the  blood-corpuscles,  which  are  true  anatomical 
elements,  take  their  origin.  There  is  furthermore  no  suffi- 
cient evidence  that  any  particular  organ  or  organs  have  the 
function  of  producing  the  blood-corpuscles.  Hewson  sup- 
posed that  they  were  formed  in  the  spleen.  Kolliker  is  of 
the  opinion  that  they  are  destroyed  in  the  spleen.  It  ia 

1  LONGET,      Traite  de  Physiologic,    tome  i.,  p.  715. 


120  THE   BLOOD. 

regarded  by  some  as  a  necessity  that  there  should  be  an  organ 
for  the  destruction  of  the  corpuscles,  and  one  for  their  forma- 
tion. Regarding  them,  as  wo  certainly  must,  as  organized 
bodies  which  are  essential  anatomical  elements  of  the  blood, 
it  is  difficult  to  imagine  what  reasons,  based  on  their  function, 
should  lead  physiologists  to  geek  so  persistently  after  an 
organ  for  their  destruction.  The  hypothesis  that  they  are 
used  in  the  formation  of  pigment  seems  hardly  sufficient  to 
account  for  this. 

In  the  present  state  of  our  science,  the  following  seem  to 
be  the  most  rational  views  with  regard  to  the  development 
and  nutrition  of  the  blood-corpuscles  : 

1.  At  their  first  appearance  in  the  ovum,  they  are  formed 
by  no  special  organs,  for  no  special  organs  exist  at  that  time, 
but  appear  by  genesis  in  the  sanguineous  blastema. 

2.  When  fully  formed,  they  are  regularly  organized  ana- 
tomical elements,  subject  to  the  same  laws  of  gradual  molec- 
ular waste  and  repair  as  any  of  the  tissues. 

3.  They  are  generated  de  novo  in  the  adult,  when  dimin- 
ished in  quantity  by  hemorrhage  or  otherwise,  and  under 
these  circumstances  they  are  probably  formed  in  the  liquor 
sanguinis  by  the  same  process  by  which  they  take  their  origin 
in  the  ovum. 

Function  of  the  Blood- Corpuscles. — Though  the  fibrin 
and  albumen  of  the  plasma  of  the  blood  are  essential  to 
nutrition,  the  red  corpuscles  are  the  parts  most  immediately 
necessary  to  life.  We  have  already  seen,  in  treating  of  trans- 
fusion, that  life  may  be  restored  to  an  animal  in  which  the 
functions  have  been  suspended  from  hemorrhage,  by  the  in- 
troduction of  fresh  blood ;  and  while  it  is  not  necessary  that 
this  blood  should  contain  fibrin,  it  has  been  shown  by  the 
experiments  of  Provost  and  Dumas  and  others,  that  the 
introduction  of  serum,  without  the  corpuscles,  has  no  resto- 
rative effect.  When  all  the  arteries  leading  to  a  part  are 
ligated,  the  tissues  lose  their  properties  of  contractility,  sen- 


LEUCOCYTES,  OR  WHITE  CORPUSCLES.          121 

sibility,  &c.,  which  may  be  restored,  however,  by  supplying 
it  again  with  the  vivifying  fluid.  We  shall  see  when  we 
come  to  treat  of  the  function  of  Respiration,  that  one  great 
distinction  between  the  corpuscular  and  fluid  elements  of  the 
blood,  is  the  great  capacity  which  the  former  have  for  absorb- 
ing gases.  Direct  observations  have  shown  that  blood  will  ab- 
sorb ten  to  thirteen  times  as  much  oxygen  as  an  equal  bulk 
of  water.  This  is  dependent  almost  entirely  on  the  presence 
of  the  red  corpuscles.1  As  all  the  tissues  are  continually 
absorbing  oxygen  and  giving  off  carbonic  acid,  a  property 
which  is  immediately  essential  to  a  continuance  of  vitality, 
a  great  function  of  the  corpuscles  is  to  carry  this  principle  to 
all  parts  of  the  body.  In  the  present  state  of  our  knowledge, 
this  is  the  only  well-defined  function  which  can  be  attributed 
to  the  red  corpuscles,  and  it  undoubtedly  is  the  principal  one. 
They  have  an  affinity,  though  not  so  great,  for  carbonic  acid, 
which,  after  the  blood  has  circulated  in  the  capillaries  of  the 
system,  takes  the  place  of  the  oxygen.  In  some  experiments 
performed  a  few  years  ago  on  the  effects  of  hemorrhage 
and  the  location  of  the  "  besoin  de  respirer"  it  wras  shown 
that  one  of  the  results  of  removal  of  blood  from  the  system, 
was  a  condition  of  asphyxia,  dependent  upon  the  absence  of 
these  respiratory  elements.2  The  following  may  then  be 
stated  as  the  principal  function  of  the  red  corpuscles  of  the 
blood : 

They  are  respiratory  organs ;  taking  up  the  greater  part 
of  the  oxygen  which  is  absorbed  by  the  blood  in  its  passage 
through  the  lungs,  and  conveying  it  to  the  tissues,  where  it 
is  given  up,  and  its  place  supplied  by  carbonic  acid. 

Leucocytes )  or  White  Corpuscles  of  the  Blood. — In  addition 
to  the  red  corpuscles  of  the  blood,  this  fluid  always  contains 
a  number  of  colorless  bodies,  globular  in  form,  in  the  sub- 

1  ROBIN  and  VERDEIL,  op.  cit.,  tome  ii.,  p.  32. 

3  See  an  article  by  the  Author  in  the  American  Journal  of  the  Medical  Sciences, 
October,  1861. 


122  THE   BLOOD. 

stance  of  which  are  embedded  a  greater  or  less  number  of 
minute  granules.  These  have  been  called  by  Robin,  Leucocytes. 
This  name  seems  more  appropriate  than  that  of  white  or 
colorless  blood-corpnscles,  inasmuch  as  they  are  not  peculiar 
to  the  blood,  but  are  found  in  the  lymph,  chyle,  pus,  and 
various  other  fluids,  in  which  ^iey  were  formerly  known  by 
different  names.  All  who  have  been  in  the  habit  of  exam- 
ining the  animal  fluids  microscopically,  must  have  noticed 
the  great  similarity  existing  between  the  corpuscular  ele- 
ments found  in  the  above-mentioned  situations.  As  mi- 
croscopes have  been  improved,  and  as  investigations  have 
become  more  exact,  the  varieties  of  corpuscles  have  been 
narrowed  down.  Now  it  is  pretty  generally  acknowledged 
that  the  corpuscles  found  in  mucus  and  pus  are  identical ; 
also  that  there  is  no  difference  between*  the  white  corpuscles 
found  in  the  lymph,  chyle,  and  blood ;  and  finally,  the  recent 
investigations  of  Robin  have  shown  that  all  of  these  bodies, 
which  were  formerly  supposed  to  present  marked  distinctive 
characters,  belong  to  the  same  class,  presenting  but  slight 
differences  in  different  situations.  The  description  which 
will  be  given  of  the  Avhite  corpuscles  of  the  blood,  and  the 
effects  of  reagents  upon  them,  will  answer,  in  the  main,  for 
all  that  are  grouped  under  the  name  of  Leucocytes.1 

Leucocytes  are  normally  found  in  the  Blood,  Lymph, 
Chyle,  Semen,  Colostrum,  and  Yitreous  Humor.  Patholog- 
ically they  are  found  in  the  secretion  of  mucous  membranes, 
after  the  slightest  irritation,  and  in  inflammatory  products, 
when  they  are  called  pus-corpuscles. 

In  examining  a  specimen  of  blood  with  the  microscope, 
we  immediately  notice  the  marked  difference  between  the 
leucocytes  and  red  corpuscles.  The  former  are  globular, 
with  a  smooth  surface,  but  rendered  somewhat  opaque  by 

1  For  a  full  account  of  the  Anatomy  and  Physiology  of  these  bodies,  the  reader 
is  referred  to  an  elaborate  article  on  this  subject  by  Robin  in  the  Journal  de  la 
Physiologic,  tome  ii.,  p.  41,  and  the  article  "Leucocyte"  in  Nysten's  Dictionary, 
Paris,  1858. 


OK  WHITE   CORPUSCLES.  123 

the  presence  of  more  or  less  granular  matter,  white,  and 
larger  than  the  red  corpuscles. 

In  examining  the  circulation  under  the  microscope,  we 
are  struck  with  the  adhesive  character  of  the  leucocytes  as 
compared  with  the  red  corpuscles.  The  latter  circulate  with 
wonderful  rapidity  in  the  centre  of  the  vessel,  while  the 
leucocytes  have  a  tendency  to  adhere  to  the  sides,  moving 
along  slowly,  and  occasionally  remaining  for  a  time  entirely 
stationary,  until  they  are  swept  along  by  a  change  in  the 
direction  or  force  of  the  current. 

Their  size  varies  somewhat,  even  in  any  one  fluid, 
as  the  blood.  Their  average  diameter  may  be  stated  as 
•g-gJy-g-  of  an  inch.  It  is  in  pus,  where  they  exist  in  greatest 
abundance,  that  their  microscopic  characters  may  be  studied 
with  greatest  advantage.  In  this  fluid,  after  it  is  discharged, 
the  corpuscles  sometimes  present  remarkable  deformities. 
They  become  polygonal  in  shape,  and  sometimes  ovoid ;  oc- 
casionally presenting  projections  from  their  surface,  which 
give  them  a  stellate  appearance.  These  alterations,  how- 
ever, are  only  temporary ;  and  after  from  twelve  to  twenty- 
four  hours,  they  resume  their  globular  shape.  On  the  addi- 
tion of  acetic  acid  they  swell  up,  become  transparent  with  a 
delicate  outline,  and  present  in  their  interior  one,  two,  three, 
or  even  four  rounded  nuclear  bodies  generally  collected  in  a 
mass.  This  is  rather  to  be  considered  as  a  coagulation  of  a 

O 

portion  of  the  corpuscle,  than  a  nucleus  brought  out  by  the 
action  of  the  acid,  which  renders  the  corpuscle  transparent ; 
though  in  some  it  is  seen  through  the  granules  without  the 
addition  of  any  reagent.  This  appearance  is  produced, 
though  more  slowly,  by  the  addition  of  water. 

Leucocytes  vary  considerably  in  their  external  characters 
in  different  situations.  Sometimes  they  are  very  pale  and 
almost  without  granulations,  while  at  others  they  are  filled 
with  fatty  granules,  and  are  not  rendered  clear  by  acetic 
acid.  As  a  rule,  they  increase  in  size  and  become  granular 
when  confined  in  the  tissues.  In  colostrum,  when  they  are 


124  THE   BLOOD. 

called  colostrum  corpuscles,  they  generally  undergo  this 
change.1  As  the  result  of  inflammatory  action,  when  they 
are  sometimes  called  inflammatory  or  exudation-corpuscles, 
leucocytes  frequently  become  much  hypertrophied,  and  are 
filled  with  fatty  granules.  They  always  retain,  however, 
general  characters  by  which  they  may  be  recognized. 

Development  of  Leucocytes. — These  corpuscles  appear 
in  the  blood-vessels  very  early  in  foetal  life,  before  the  lym- 
phatics can  be  demonstrated.  They  arise  in  the  same  way 
as  the  red  corpuscles,  by  genesis  from  materials  existing  in 
the  vessels.  They  appear  in  lymphatics,  before  wre  come  to 
the  lymphatic  glands,  and  in  the  foetus  anterior  to  the  devel- 
opment of  the  spleen,  and  also  on  the  surface  of  mucous 
membranes ;  so  they  cannot  be  considered  as  produced  exclu- 
sively by  these  glands,  as  has  been  supposed.  There  is  no 
organ  nor  class  of  organs  in  the  body  specially  charged 
wTith  their  formation ;  and  though  frequently  a  result  of  in- 
flammation, this  process  is  by  no  means  necessary  for  their 
production.  Robin 2  has  carefully  noted  the  phenomena  of 
their  development  in  recent  wounds.  The  first  exudation 
consists  of  clear  fluid,  with  a  few  red  corpuscles ;  then  a 
finely  granular  blastema.  In  from  a  quarter  of  an  hour  to  an 
hour,  pale  transparent  globules,  -g-^oir  to  -g-gVo  of  an  inch  in 
diameter,  make  their  appearance,  which  soon  become  finely 
granular,  and  present  the  ordinary  appearance  of  leucocytes. 
They  are  thus  developed,  like  other  anatomical  elements,  by 


1  Colostrum  is  the  discharge  from  the  mammary  glands,  occurring  during  the 
first  few  days  after  delivery,  which  precedes  the  full  establishment  of  the  lacteal 
secretion.  It  is  a  serous  fluid,  rather  clear,  which  presents,  on  microscopical 
examination,  a  few  milk-globules,  large  drops  of  oil,  rounded  masses  of  small 
fatty  granules,  and  enlarged  and  granular  leucocytes,  called  colostrum- corpuscles, 
as  well  as  those  which  have  undergone  no  alteration.  These  gradually  disappear, 
as  the  secretion  is  established,  and  their  place  is  supplied  by  the  milk-globules. 
(See  Colostrum,  Nysten's  Dictionary,  by  Littre  and  Robin ;  Paris,  1858.) 

8  Loc.  cit. 


OB   WHITE   CORPUSCLES.  125 

organization  of  the  necessary  elements  furnished  by  a  blas- 
tema, and  not  by  the  action  of  any  special  organ  or  organs. 

The  quantity  of  leucocytes  compared  to  the  red  corpuscles 
can  only  be  given  approximately.  It  has  been  estimated  by 
counting  under  the  microscope  the  red  corpuscles  and 
leucocytes  contained  in  a  certain  space.  Moleschott1  gives 
the  proportion  as  1 :  335 ;  others  at  from  1 :  300  to  1 :  500. 
It  has  been  found  by  Dr.  E.  Hirt,  of  Zittau,  whose  obser- 
vations have  been  confirmed  by  others,  that  the  relative 
quantity  of  leucocytes  is  much  increased  during  diges- 
tion. He  found  in  one  individual  a  proportion  of  1 : 
1800  before  breakfast;  an  hour  after  breakfast,  which  he 
took  at  8  o'clock,  1 :  TOO ;  between  11  and  1  o'clock,  1 :  1500 ; 
after  dining  at  1  o'clock,  1 : 400  ;  two  hours  after,  1 :  1475  ; 
after  supper  at  8  P.  M.,  1:550;  at  11 J  P.  M.,  1 : 1200.2  The 
leucocytes  are  much  lighter  than  the  red  corpuscles,  and  when 
the  blood  coagulates  slowly,  are  frequently  found  forming  a 
layer  on  the  surface  of  the  clot,  which  is  called  the  "  buffy 
coat." 

Numerous  observers,  among  whom  may  be  mentioned 
Donne,  Kolliker,  Gray,  and  Hirt,3  have  noticed  a  great  in- 
crease in  the  number  of  leucocytes  in  the  blood  coming  from 
the  spleen,  and  have  supposed  that  they  are  chiefly  manufac- 
tured in  this  organ.  It  is  inconsistent  with  the  mode  of 
development  of  these  corpuscles  to  suppose  that  any  special 
organ  is  exclusively  engaged  in  their  production ;  and  their 
persistence  in  animals  after  extirpation  of  the  spleen  shows 
that  they  are  developed  in  other  situations. 

The  function  of  the  leucocytes  is  not  understood.  The 
supposition  that  they  break  down  and  become  nuclei  for  the 
development  of  red  corpuscles,  which  at  one  time  obtained, 
is  a  pure  hypothesis,  and  has  no  basis  in  fact. 

1  KOLLIKER,  Manual  of  Microscopic  Anatomy,  London,  1860,  p.  521. 

2  MILNE-EDWARDS,  Lecons  our  la  Physiologic  et  V Anatomic  Comparec^  tome 
i.,  p.  350. 

3  Ibid.,  p.  353. 


126  THE   BLOOD. 

Elementary  Corpuscles. — Little  granules  are  found  in  the 
blood,  especially  during  digestion,  which,  as  they  were 
supposed  to  take  part  in  the  formation  of  the  white  corpuscles, 
have  been  called  elementary  granules  or  corpuscles.  They 
are  little  fatty  particles  of  the  chyle  which  come  from  the 
thoracic  duct,  and  are  not  positively  known  to  have  any  con- 
nection with  the  formation  of  the  other  corpuscular  elements 
of  the  blood. 


CHAPTER  II. 

COMPOSITION    OF   THE   BLOOD. 

General  considerations — Methods  of  quantitative  analysis — Fibrin — Corpuscles — 
Albumen — Inorganic  constituents — Sugar — Fatty  emulsion — Coloring  matter 
of  the  serum — Urea  and  the  Urates — Cholesterine — Creatine — Creatinine. 

ASSUMING,  as  we  certainly  must,  that  the  blood  furnishes 
material  for  the  nourishment  of  all  the  tissues  and  organs,  we 
expect  to  find  entering  into  its  composition  all  the  proximate 
principles  existing  in  the  body  which  undergo  no  change  in 
nutrition,  like  the  inorganic  principles,  and  organic  matters 
which  are  capable  of  being  converted  into  the  organic  ele- 
ments of  every  tissue.  Furthermore,  as  the  products  of  waste 
are  all  taken  up  by  the  blood  before  their  final  elimination, 
these  also  should  enter  into  its  composition.  With  these 
great  principles  in  our  minds,  it  is  unnecessary  to  insist  upon 
the  importance  of  accurate  proximate  analyses  of  the  circu- 
lating fluid.  It  is  not  many  years  that  our  knowledge  of 
the  laws  of  nutrition  and  destructive  assimilation  have  enabled 
us  to  appreciate  the  full  importance  of  the  blood ;  but  it  has 
been  so  palpable  that  this  fluid  is  necessary  to  life,  that  the 
older  physiologists  made  numberless  futile  attempts  to  obtain 
some  clear  idea  of  its  composition.  "We  have  only  to  go 
back  to  the  beginning  of  the  present  century  to  find  the  first 
analyses  of  the  blood  which  were  attended  with  any  degree 
of  success.  In  1808,  Berzelius  analyzed  the  serum  of  the 


128  THE   BLOOD. 

human  blood,  indicating  certain  proportions  of  albumen, 
lactate  of  soda,  muriate  of  soda,  etc. ;  lie  was  followed  by 
Marcet  in  1811,  by  whom  his  observations  were  confirmed. 
In  1823,  Provost  and  Dumas  published  their  elaborate  re- 
searches into  the  composition  of  the  blood,  which  seemed  to 
give  an  impulse  to  investigations  in  this  direction,  and  were 
soon  followed  by  the  analyses  of  Andral  and  Gavarret,  Leh- 
mann,  Simon,  Becquerel  and  Rodier,  Denis,  and  a  host  of 
others,  whose  labors  have  made  us  comprehend  some  of  the 
most  important  laws  which  regulate  the  general  processes  of 
nutrition. 

Notwithstanding  the  immense  amount  of  labor  bestowed 
by  the  most  eminent  chemists  of  the  day  upon  the  quantita- 
tive analysis  of  the  blood,  and  the  great  physiological  interest 
attaching  to  every  advance  in  our  knowledge  in  this  direction, 
the  difficulties  in  the  way  are  so  great,  that  even  now  there 
are  no  analyses  which  give  the  exact  quantities  of  each  of  its 
inorganic  constituents.  This  is  owing  to  the  great  difficulty 
in  the  analysis  of  any  fluid  in  which  inorganic  and  or- 
ganic principles  are  so  closely  united ;  for  there  is  no  more 
delicate  problem  in  analytical  chemistry  than  the  determina- 
tion of  the  presence  and  quantities  of  inorganic  substances 
united  with  organic  matter.  Of  the  animal  fluids  which  are 
easily  obtained,  the  blood,  from  the  large  proportion  of  differ- 
ent organic  principles  which  enter  into  its  composition,  presents 
the  greatest  difficulties  to  the  analytical  chemist.  Another 
difficulty  presents  itself  in  the  necessity  of  &  proximate,  and  not 
an  ultimate  analysis.  It  is  not  sufficient  to  give  the  amount 
of  certain  chemical  elements  which  the  blood  contains ;  we 
must  ascertain  the  amount  of  these  elements  in  the  state  of 
union  with  each  other  to  form  proximate  principles. 

Analyses  have  shown  that  the  constituents  of  the  blood 
may  be  divided  into  : 

1.  Inorganic  Constituents. — These  exist  in  a  state  of  inti- 
mate and  molecular  union  with  the  organic-nitrogenized  ele- 


COMPOSITION  OF   THE  BLOOD.  129 

ments.  Their  presence  is  indicated  by  the  appropriate  tests 
applied  to  the  residue  of  the  blood  after  incineration,  which 
show  the  well-known  reactions  of  the  chlorides,  sulphates, 
phosphates,  and  carbonates,  with  sodium,  potassium,  lime, 
magnesia,  and  iron.  In  addition  we  have  certain  gases 
(oxygen,  nitrogen,  and  carbonic  acid),  which  may  be  extracted 
by  the  air-pump  or  by  displacement. 

2.  Organic,  Non-nitrogenized,   Constituents.  —  These  are 
the  sugars  and  fats ;  which  are  separated  from  the  other  ele- 
ments without  much  difficulty,  and  may  be  recognized  by 
their  peculiar  properties. 

3.  Organic,  Nitrogenized  Constituents. — These  constitute 
the  greater  part  of  the  blood,  and  are  inseparably  connected, 
in  their  functions,  and  as  a  condition  of  existence,  with  the 
inorganic  principles.     They  may  be  extracted  by  processes 
already  described  in  treating  of  fibrin,  albumen,  and  globu- 
line,  and  recognized  by  their  peculiar  properties. 

Most  of  the  constituents  of  the  blood  are  found  both  in 
the  corpuscles  and  plasma.  It  is  difficult  to  determine  the 
different  constituents  of  these  two  parts  of  the  blood.  It  has 
been  shown,  however,  by  Schmidt,  of  Dorpat,  that  the  phos- 
phorized  fats  are  more  abundant  in  the  globules,  while  the 
fatty  acids  are  more  abundant  in  the  plasma.  The  salts  with 
a  potash  base  have  been  found  by  the  same  observer  to  exist 
almost  entirely  in  the  corpuscles,  and  the  soda  salts  are  four 
times  more  abundant  in  the  plasma  than  in  the  corpuscles/ 
All  the  iron  exists  in  the  red  corpuscles. 

The  proportions  of  the  various  constituents  of  the  blood 
are  subject  to  certain  variations.  These  points,  with  their 
relations  to  the  tissues  in  the  processes  of  nutrition,  have 
been  so  fully  taken  up  in  the  consideration  of  Proximate 
Principles,  that  they  do  not  demand  special  notice  in  this 


1  MILNE-EDWARDS,     Le$ons  sur  la  Physiologic,    etc.,  tome  i.,  p.  225. 
9 


ISO  THE   BLOOD. 

connection.  In  addition  to  the  nutritive  principles,  we  have 
entering  into  the  composition  of  the  blood,  urea,  cholesterine, 
urate  of  soda,  creatine,  creatinine,  and  other  substances,  the 
characters  of  which  are  not  yet  fully  determined,  belonging 
to  the  class  of  JExcrementitious  Principles.  Their  considera- 
tion comes  more  appropriately*under  the  head  of  Excretion, 
and  they  will  be  fully  taken  up  in  the  chapter  devoted  to 
that  subject.  Though  a  knowledge  of  the  exact  proportions 
of  the  various  elements  of  the  blood  is  not  necessary  in  order 
to  appreciate  the  relations  of  this  fluid  to  the  tissues,  the 
great  interest  which  is  attached  to  this  line  of  investigation, 
and  the  important  advantages  which  we  may  look  for  in  the 
future  from  extended  inquiry  in  this  direction,  lead  us  to 
discuss  at  some  length  the  methods  which  have  been  employ- 
ed by  physiological  chemists  in  quantitative  analyses,  with 
some  of  the  results  which  have  already  been  obtained. 


Quantitative  Analysis  of  the  Blood. 

The  methods  which  have  been,  and  are  now,  commonly 
employed  for  quantitative  analysis  of  the  blood  vary  very 
little  from  the  process  recommended  by  Provost  and  Dumas 
in  1823.  They  are  based  upon  the  supposition  that  the 
organic  constituents,  fibrin  and  albumen,  are  solid  substances 
in  solution  in  the  watery  elements,  and  that  all  the  water  of 
the  blood  is  to  be  attributed  to  the  serum.  As  we  have  shown 
in  treating  of  organic  substances  that  this  view  of  their  con- 
dition in  the  fluids  is  erroneous,  and  that  the  desiccated  ma- 
terials obtained  from  the  blood  do  not  represent  the  real 
quantities  of  its  organic  elements,  a  new  method  of  analysis, 
based  on  the  view  that  these  principles  are  naturally  fluid, 
seems  necessary.  The  same  process  has  been  employed  for 
the  estimation  of  the  proportion  of  corpuscles.  Here  the 
error  is  too  manifest  to  require  discussion.  It  is  evident  that 
the  blood-corpuscles  are  semi-solid  bodies  which  become 
altered  by  desiccation ;  and  an  estimate  which  does  not  give 


QUANTITATIVE   ANALYSIS.  131 

their  weight  in  their  natural  moist  condition,  gives  us  no  idea 
of  their  real  proportion.  So  apparent  has  this  been  to  phy- 
siological chemists,  that  attempts  have  been  made  by  Denis, 
Schmidt,  Yierordt,  Figuier,  and  others  to  estimate  the  moist 
corpuscles;  but  in  attempting  to  attain  extreme  accuracy, 
these  observers  have  almost  entirely  failed,  and  their  ideas  of 
the  real  proportion  of  the  corpuscles  are  merely  conjectural. 
These  remarks  only  apply  to  researches  into  the  organic 
constituents  of  the  blood.  The  analyses  with  reference  to  the 
inorganic  elements,  though  they  have  not  yet  shown  us  the 
exact  proportion  of  each  one  of  them,  are  of  course  accurate 
as  far  as  they  go. 

The  various  processes  for  analysis  of  the  blood  now  em- 
ployed by  chemists  do  not  differ  very  much.  As  one  of  the 
best,  we  may  take  that  recommended  by  Becquerel  and  Ro- 
dier,  who  are  perhaps  as  high  authority  on  this  subject  as 
any.  Their  process,  which  we  give  in  its  essential  particulars, 
has  an  advantage  over  most  others  in  simplicity. 

Two  specimens  of  blood  are  taken  and  carefully  weighed ; 
one  of  them  is  defibrinated,  the  fibrin  collected,  dried,  and 
weighed,  which  gives  the  proportion  of  fibrin.  The  other 
is  set  aside  to  coagulate.  A  known  weight  of  the  defibrinated 
blood  is  then  evaporated  to  dryness,  and  the  proportion  of 
dry  residue  carefully  estimated.  The  residue  is  then  calci- 
nated to  give  the  proportions  of  inorganic  constituents,  which 
remain  after  the  organic  matters  have  become  volatilized. 
After  the  blood  set  aside  to  coagulate  has  separated  into  clot 
and  serum,  a  definite  quantity  of  the  serum  is  evaporated  to 
dryness  and  the  residue  estimated.  As  the  dry  residue  of  the 
defibrinated  blood  contains  the  solid  matters  of  the  serum  + 
the  dried  corpuscles — the  proportion  per  1,000  parts  of  the 
solid  matters  of  the  defibrinated  blood — the  proportion  per 
1,000  parts  of  the  solid  matters  of  the  serum,  would  give  the 
proportion  of  corpuscles. 

We  thus  have  obtained  the  proportions  of  water,  of  inor- 
ganic matter,  of  corpuscles,  and  of  fibrin.  The  next  step  is 


132  THE   BLOOD. 

to  estimate  the  albumen,  fatty,  and  extractive  matter.  For 
this  purpose  we  desiccate  a  known  quantity  of  serum,  care- 
fully pulverize  the  dry  residue,  and  treat  it  repeatedly  with 
boiling  water  till  it  has  washed  out  all  soluble  matters. 
These  are  undetermined  extractive  matters,  and  free  salts 
in  solution  in  the  serum.  Tke  residue,  thus  treated  with 
boiling  water,  is  desiccated  and  treated  several  times  with 
boiling  alcohol,  which  dissolves  all  the  fatty  substances.  The 
insoluble  residue  is  then  dried  and  weighed,  and  represents 
pure  albumen,  which,  it  will  be  remembered,  is  not  affected 
by  boiling  water  or  alcohol.  The  loss  after  treating  with 
boiling  alcohol  gives  the  quantity  of  fatty  matters.  The  pro- 
portions of  inorganic  matters  are  obtained  by  analysis  of  the 
residue  after  incineration.  It  is  unnecessary  to  describe 
the  complicated  and  difficult  manipulations  involved  in  this 
process.1 

1  The  above  is  condensed  from  BECQUEREL  and  RODIER,  "  Traite  de  Chimie 
Pathologique  appliquee  d  la  Medecine  Pratique"  Paris,  1854,  page  21  et  seq.  As 
the  result  of  analyses  of  the  blood  of  twenty-two  healthy  persons,  they  give  the 
following  table,  page  86.  The  list  of  inorganic  salts  is  taken  from  pages  65,  66, 
and  67. 

DENSITY  OF  THE  BLOOD 1060 

COMPOSITION. 

Water 781-600 

Globules 135-000 

Albumen 70-000 

Fibrin  . . . . 2-500 

Seroline 0-025 

Cholesterine . 0*125 

Oleate,  margarate,  and  stearate  of  soda 1-400 

Chlorides  of  sodium,  potassium,  and  magnesium 3-500 

Carbonate  of  soda... 

Free  soda 

Sulphate  of  s'oda 

Phosphate  of  soda... 


(Carbonate  of  soda  most  abundant)  ....        2'COO 


Carbonate  of  potassa  .... 

Sulphate  "         

Phosphate         "         .... 
Sulphate  of  magnesia. . . . 

Phosphate  of  lime j  t\ar\ 

Phosphate  of  magnesia  . .  j  " 

Iron 0-550 

Undetermined  extractive  matters 2*450 

1,000-000 


QUANTITATIVE  ANALYSIS.  133 

The  above  process  is  perhaps  as  simple  and  reliable  as 
any ;  but  of  course  each  chemist  has  some  slight  modifica- 
tions. By  some  the  globules  are  estimated  by  drying  the  clot 
after  coagulation  and  deducting  the  weight  of  the  fibrin. 
Some  recommend  to  expose  the  fibrin  after  desiccation  to  in- 
cineration, and  deduct  the  weight  of  the  residue  of  inorganic 
matter.  All  of  the  processes,  however,  are  materially  the 
same,  and  differ  but  little  from  that  employed  by  Provost  and 
Dumas.  As  before  remarked,  the  results,  as  regards  the  fatty 
and  inorganic  constituents  of  the  blood,  are  as  accurate  as 
possible  with  our  present  means  of  investigation ;  and  the 
comparative  results,  in  analyses  of  the  blood  for  fibrin,  albu- 
men, and  corpuscles  in  health  and  disease,  which  have  crowned 
the  labors  of  Andral  and  Gavarret,  Becquerel  and  Rodier, 
and  a  number  of  others,  are  of  permanent  value.  But  a 
glance  at  the  process,  and  the  quantities  given  for  the  fibrin, 
albumen,  and  corpuscles,  indicate  that  the  whole  is  inconsist- 
ent with  our  ideas  of  the  condition  under  which  these  sub- 
stances exist  in  the  body.  Microscopic  examination  shows 
that  at  least  one-half  the  mass  of  the  blood  consists  of  cor- 
puscles, while  analysis  gives  only  135  parts  per  1,000.  The 
fibrin  of  the  blood  is  sufficient  to  entangle,  as  it  coagulates, 
all  the  corpuscles,  and  with  them  form  the  clot ;  yet  we  are 
told  that  its  proportion  is  2*5  parts  per  1,000.  We  boil  the 
serum,  the  albumen  changes  from  a  fluid  to  a  semi-solid  con- 
dition, and  the  whole  mass  is  solidified ;  yet  the  estimate  of 
its  proportion  is  70  parts  per  1,000.  The  fact  is  that  these 
estimates  give  us  only  the  dry  residue  of  the  organic  princi- 
ples ;  and  to  form  an  idea  of  their  actual  proportion,  we  should 
estimate  them,  if  possible,  with  their  water  of  composition, 
and  united  with  the  inorganic  salts,  which  cannot  be  separated 
from  them  without  incineration  and  consequent  destruction. 

With  this  end  in  view,  and  for  want  of  a  better  process,  we 
may  employ  the  following  mode  of  analysis,  which  is  easy  of 
application,  and  sufficiently  accurate  for  all  practical  purposes.1 

1  See  an  article  by  the  author,  on  The  Organic  Nilrogenized  Principles  of  the 


134  THE   BLOOD. 

The  blood  to  be  analyzed  is  taken  from  the  arm,  and  re- 
ceived into  two  carefully  weighed  vessels.  The  quantity  in 
each  vessel  may  be  from  two  to  four  ounces.  One  of  the 
specimens  is  immediately  whipped  with  a  small  bundle  of 
broom-corn,  previously  moistened  and  weighed,  so  as  to  col- 
lect the  fibrin ;  and  after  the  fibrin  is  completely  coagulated, 
the  whole  is  carefully  weighed,  deducting  the  weights  of  the 
vessel  and  broom-corn,  which  gives  the  weight  of  the  specimen 
of  blood  used.  The  other  specimen  is  set  aside  to  coagulate. 

The  first  specimen  is  used  in  the  estimation  of  the  fibrin 
and  corpuscles ;  the  second  is  set  aside  to  coagulate,  and  is 
used  to  estimate  the  albumen.  It  is  important  to  cover  the 
vessels  as  soon  as  the  blood  is  drawn,  for,  as  has  been  demon- 
strated by  Becquerel  and  Rodier,  blood  exposed  to  the  air 
loses  weight  rapidly  by  evaporation.1 

We  now  pass  the  first  specimen  of  blood  through  a  fine 
sieve  to  collect  any  fibrin  that  may  not  have  become  attached 
to  the  wisp,  strip  the  fibrin  from  the  wisp,  and  wash  it  under 
a  stream  of  water.  This  may  be  done  very  rapidly  if  we 
cause  the  water  to  flow  through  a  small  strainer,  by  which  it 
is  broken  up  into  a  number  of  little  streams,  and  knead  the 
fibrin  with  the  fingers,  doing  this  over  a  sieve  so  as  to  catch 
any  particles  that  may  become  detached.  In  this  way  it 
may  be  freed  from  the  corpuscles  in  five  or  ten  minutes.  The 
fibrin  is  then  freed  from  most  of  the  adherent  moisture  by 
bibulous  paper,  and  weighed  as  soon  as  possible.  By  the 
following  formula  we  estimate  the  proportion  per  1,000  parts 
of  blood : 

Weight  of  blood  used  :  Weight  of  fibrin  :  :  1,000  :  Fi- 
brin per  1,000. 

The  next  step  is  to  estimate  the  corpuscles.  For  this  pur- 
pose a  portion  of  the  defibrinated  blood,  which  is  carefully 

Body,  with  a  New  Method  for  their  Estimation  in  the  Blood,  American  Journal 
of  the  Medical  Sciences,  October,  1863. 
1  Op.cit.,  p.  31. 


QUANTITATIVE   ANALYSIS.  135 

weighed,  is  mixed  with  twice  its  volume  of  a  saturated  solu- 
tion of  sulphate  of  soda,  and  thrown  upon  a  filter  which  has 
been  carefully  weighed  and  moistened  with  distilled  water, 
and  also,  just  before  receiving  the  mixture  of  blood  and 
sulphate  of  soda,  with  the  saline  solution.  The  fluid  which 
passes  through  should  be  about  the  color  of  the  serum ;  if  a 
few  corpusles  pass  at  first,  the  liquid  should  be  poured  back 
until  it  becomes  clear.  The  funnel  is  then  covered,  and  the 
fluid  allowed  to  separate,  the  blood-corpuscles  being  retained 
on  the  filter.  The  filter  and  funnel  are  then  plunged  several 
times  into  a  vessel  of  boiling  water,  by  which  all  the  sulphate 
of  soda  which  remains  is  washed  out,  and  the  corpuscles  are 
coagulated  without  changing  in  weight.  The  funnel  should 
be  again  covered  and  the  water  allowed  to  drip  from  the 
filter,  after  which  it  is  weighed,  deducting  the  weight  of  the 
moist  filter  previously  obtained,  which  gives  us  the  weight 
of  the  corpuscles.  We  obtain  the  proportion  of  corpuscles 
to  1,000  parts  of  blood  by  the  following  formula  : 

Defibrinated  blood  used  :  Corpuscles  :  :  Defibrinated 
blood  per  1,000  :  Corpuscles  per  1,000. 

The  next  step  is  to  estimate  the  quantity  of  albumen  in 
the  serum,  and  thence  its  proportion  in  the  blood.  Fo'r  this 
purpose  we  first  ascertain  the  quantity  of  serum  in  1,000 
parts  of  blood,  which  is  done  by  subtracting  the  sum  of  the 
fibrin  and  corpuscles  per  1,000  from  1,000.  Having  done  this, 
and  waited  ten  or  twelve  hours  for  specimen  "No.  2  to  sepa- 
rate completely  into  clot  and  serum,  we  take  a  small  quan- 
tity of  the  serum,  about  half  an  ounce,  weigh  it  carefully, 
and  add  suddenly  twice  its  volume  of  absolute  alcohol.  The 
albumen  will  be  thrown  down  in  a  grumous  mass,  and  the 
whole  is  thrown  upon  a  filter,  Avhich  has  been  previously 
moistened  with  alcohol  and  weighed.  The  funnel  is  imme- 
diately covered,  and  the  fluid  separates  from  the  albumen 
very  rapidly.  "We  ascertain  that  no  fluid  albumen  passes 
through  the  filter  by  testing  the  fluid  with  nitric  acid.  After 


136  THE    BLOOD. 

the  filter  has  ceased  to  drip,  it  is  weighed,  and  the  weight  of 
the  albumen  ascertained  by  deducting  the  weight  of  the  filter. 
The  proportion  of  albumen  to  1,000  parts  of  blood  is  obtained 
by  the  following  formula : 

Serum  used  :  Albumen  :  :  Serum  per  1,000  :  Albumen 
per  1,000. 

The  above  process,  which  has  been  described  in  detail  in 
the  hope  that  it  may  be  employed  by  others  in  analysis  of 
the  blood  for  its  organic  constituents,  has  at  least  the  advan- 
tage of  simplicity  and  facility  of  application.  As  regards 
accuracy,  having  repeatedly  made  analyses  of  different  por- 
tions of  the  same  fluid  with  almost  identical  results,  it  has 
seemed  sufficiently  exact  for  all  practical  purposes.  As  an 
example  we  may  mention  an  analysis  of  two  equal  portions  of 
defibrinated  blood  (34*20  grammes)  for  corpuscles  ;  one  speci- 
men gave  16*4:0,  and  the  other  16*43  grammes.  This  part  of  the 
process  would  seem  more  open  to  the  objection  of  inaccuracy 
than  any,  yet  the  difference  of  the  result  in  the  two  analyses  is 
so  slight  that  it  may  be  disregarded.  Repeated  examinations 
of  different  specimens  of  the  same  serum  for  albumen  were 
followed  by  identical  results.1  While  the  exceeding  accu- 
racy which  is  desired  by  chemists,  and  is  necessary  in  many 
analyses,  is  not  attainable  in  such  examinations  as  these,  it  is 
not  even  desirable ;  for  as  physiologists  we  must  see  that 
even  an  approximation  of  the  proportions  of  the  organic 
matters,  as  they  really  exist,  is  better  than  the  most  accu- 
rate estimate  of  their  dry  residue.  In  taking  the  weights, 
the  only  point  is  to  do  it  rapidly  and  avoid  loss  by  evapo- 
ration. If  this  be  borne  in  mind,  and  care  be  taken  in  differ- 
ent examinations  to  weigh  the  principles  at  the  same  stage 
of  the  operation,  the  simplicity  of  the  process  should  make  it 
valuable  in  comparative  analyses  of  the  blood  in  different 
conditions  of  the  system. 

In    estimating    the  proportion   of  fibrin,   the   ordinary 

1  American  Journal  of  the  Medical  Sciences,  loc.  cit. 


QUANTITATIVE   ANALYSIS.  137 

method  is  followed,  with  the  exception  that  the  weight  of  the 
moist  fibrin  is  taken  instead  of  the  dry  residue. 

In  estimating  the  corpuscles,  after  a  number  of  trials,  the 
process  recommended  by  Figuier  was  adopted,  with  a  similar 
modification.  Figuier  dried  the  corpuscles  after  separating 
them  from  the  serum  by  filtration,  taking  advantage  of  the 
property  of  sulphate  of  soda,  which  retains  them  on  the  filter. 
He  employed  this  method  to  separate  the  corpuscles  com- 
pletely, and  investigate  their  chemical  constitution.1 

In  estimating  the  albumen,  the  object  was,  as  in  the  case 
of  the  other  principles,  to  obtain  it  as  nearly  as  possible  in  its 
natural  condition,  simply  changing  its  form  from  fluid  to 
semi-solid,  without  adding  any  thing  which  would  decompose 
it,  or  unite  with  it.  For  this  purpose  absolute  alcohol  seemed 
better  than  heat,  nitric  acid,  the  galvanic  current,  or  any  other 
agents  by  which  it  is  coagulated. 

If  the  different  organic  principles  be  incinerated,  the  ash 
will  present  the  characteristic  reactions  of  the  chlorides,  sul- 
phates, phosphates,  etc.,  inorganic  principles,  which,  as  we 
have  already  seen,  cannot  be  separated  from  the  organic  con- 
stituents of  the  body  without  destruction  of  the  latter. 

The  blood  of  a  healthy  male,  set.  27  years,  weight  170 
pounds,  who  had  never  suffered  from  disease,  taken  from  the 
arm  at  1  p.  M.,  the  last  meal  having  been  taken  at  8  A.  M., 
furnished  the  proportions  of  organic  constituents  given  in  the 
following  table.  To  complete  the  table,  the  proportions  of 
inorganic  principles,  fats,  etc.,  were  taken  from  the  analyses 
of  Becquerel  and  Rodier,  to  which  reference  has  already  been 
made.  The  proportion  of  water  is  estimated  by  subtracting 
the  sum  of  the  solid  and  semi-solid  constituents  from  the 
entire  weight  of  the  blood.2 

1  Sur  une  Method*  nouvelle  pour  V Analyse  du  Sang,  et  sur  la  Constitution 
chimique  des  Globules  mnguins.  Par  M.  L.  FIGUIER.  (Ann.  de  Chim.  et  de  Phys., 
1844,  3m«  serie,  tome  xi.,  p.  506.) 

2  Further  details  of  experiments  on  this  subject  are  contained  in  the  article,  to 
which  reference  has  been  made,  in  the  •'  American  Journal,"  October,  1 863. 


138  THE    BLOOD. 


Composition  of  the 

Water 154-870 

Corpuscles , . . .  495-590 

Albumen 329-820 

Fibrin 8'820 

Seroline(?) 0'025 

Cholesterine 0-125 

Oleate,  margarate,  and  stearate  of  soda. .  .T 1*400 

Chloride  of  sodium,  ) 

potassium  (a  trace),  f 

Carbonate  of  soda 

Free  soda 

Sulphate  of  soda 

^OMteoflSSia:.     \  (Carbonate  of  soda  most  abundant), 
Sulphate  of  potassa... 
Phosphate  of  potassa. 
Sulphate  of  magnesia. 

Phosphate  of  lime 

Phosphate  of  magnesia. 

Iron 0*550 

Undetermined  extractive  matters 2-450 


0-350 


1,000-000 

There  exist  in  the  blood  certain  well-determined  principles 
not  given  in  the  above  table,  some  of  which  have  great  physio- 
logical importance ;  and  it  is  to  be  expected  that  further 
investigations  will  reveal  others,  among  what  are  now  called 
extractive  matters,  an  acquaintance  with  which  will  mate- 
rially advance  our  pathological,  as  well  as  our  physiological 
knowledge  of  this  fluid.  The  developments  of  the  last  few 
years  with  regard  to  urea  and  cholesterine  lead  us  to  look 
for  the  discovery  of  new  principles,  variations  from  the  nor- 
mal proportions  of  which  will,  perhaps,  be  found  to  constitute 
important  pathological  conditions.  In  both  a  physiological 
and  pathological  point  of  view,  there  is  much  to  be  done  in 
this  line  of  investigation. 

Aside  from  the  gases^  we  are  now  acquainted  with  the 

1  For  purposes  of  comparison,  the  fibrin,  albumen,  and  corpuscles  were  desic- 
cated and  weighed,  giving  the  following  proportions  of  dry  residue : 
Fibrin,  2-50  parts  per  1,000  of  fresh  blood. 

Albumen,       71 '5  3        do.  do. 

Corpuscles,  125*00         do.  do. 


QUANTITATIVE   ANALYSIS.  139 

following  additional  principles  in  the  blood,  which  are  either 
constant  or  temporary  constituents :  Sugar,  Fatty  Emulsion,  a 
Coloring  Matter  peculiar  to  the  serum,  Urea,  Uric  Acid  in 
combination,  Cholesterine,  Creatine,  and  Creatinine. 

Sugar. — Bernard '  showed  in  1848  that  sugar  always  exists 
in  the  blood  of  the  hepatic  veins  and  the  right  side  of  the 
heart.  It  is  manufactured  by  the  liver,  and  disappears  in  the 
lungs.  When  its  production  is  most  active,  as  in  full  diges- 
tion, it  may  exist  in  small  quantity  in  the  arterial  blood. 
Ordinarily  it  is  only  to  be  found  in  the  blood  between  the 
liver  and  the  lungs,  except  when  it  exists  in  the  blood  of  the 
portal  vein,  after  the  ingestion  of  saccharine  or  starchy 
matters. 

Fatty  Emulsion. — After  a  full  meal  with  an  abundance 
of  fat,  the  blood  contains  a  considerable  proportion  of  fatty 
emulsion.  Bernard2  has  shown,  also,  that  the  blood  of  the 
hepatic  veins  contains  an  emulsive  substance  which  is 
formed  by  the  liver.  "We  have  already  seen  that  the  blood 
corpuscles  contain  a  certain  proportion  of  fatty  matter  in  a 
state  of  molecular  union  with  the  organic  nitrogenized  prin- 
ciples. 

Coloring  Matter  of  the  Serum. — The  serum  has  a  yellowish 
color,  more  or  less  intense,  which  is  dependent  upon  a  pecu- 
liar coloring  matter.  This  has  never  been  isolated,  but  is 
thought  by  some  to  be  identical  with  the  coloring  matter  of 
the  bile,3  a  supposition,  however,  which  does  not  seem  very 
probable. 

1  Recherches  sur  une  Nouvelle  Fonction  du  Fole  considers  comme  Organe 
Producteur  de  Mature  Sucree    chez  THomme  et  les  Animauz.     These.     Paris, 
1853. 

2  See  page  64. 

3  BECQUEREL    and  RODIER,  .Recherches  sur   la    Composition  du  Sang  dans 
Tetat  de  Sante  et  dans  Vetat  de  Maladie,  Paris,  1844. 


140  THE   BLOOD. 

Urea  and  the  Urates. — In  1821  Prevost  and  Dumas  l 
discovered  urea  in  the  blood  of  auimals  from  which  the 
kidneys  had  been  removed  ;  which  was  the  first  experimental 
demonstration  that  this  principle  is  formed  in  the  system  and 
eliminated  by,  not  manufactured  in,  the  kidneys.  It  was 
demonstrated  in  healthy  blood*  by  Marchand,2  in  1838,  and 
since  then  has  been  recognized  as  one  of  its  normal  constit- 
uents, though  existing  in  very  minute  quantity.  These 
observations  have  been  confirmed  by  numerous  French,  Ger- 
man, and  English  physiologists.  The  urate  of  soda  also  exists 
in  small  quantity  in  the  blood,  and  possibly  the  hippurate  of 
soda.  The  reason  why  the  proportion  of  these  principles  is 
so  small,  is  that  they  are  eliminated  by  the  proper  organs  as 
soon  as  formed. 

Cholesterine. — This  substance  was  demonstrated  in  the 
blood  by  Denis  in  1830.3  It  is  now  known  to  exist  in  this 
fluid  in  considerable  quantity.  It  is  most  abundant  in  the 
blood  coming  from  the  nervous  centres,  where  it  is  produced 
in  great  part,  and  is  diminished  in  the  passage  of  the  blood 
through  the  liver/ 

A  substance  was  described  by  Boudet  in  1833,  in  the 
blood,  which  he  called  Seroline.  Its  existence  in  the  blood 
is  problematical.6 

Creatine  and  Creatinine. — Yerdeil  and  Marcet  have  de- 
monstrated the  presence  of  these  substances  in  the  blood.' 
Their  proportion  is  very  small,  and  has  not  been  determined. 
They  undoubtedly  have  the  same  relation  to  the  system  as 
urea  and  cholesterine. 

1  Annales  de  Chimie  et  de  Physique,  1821,  tome  xviii.,  p.  280. 
a  Annales  des  Sciences  Naturelles,  1838,  2me  serie,  tome  x.,  p.  46. 

3  ROBIN  and  VERDEIL,  op.  cit.,  tome  iii.,  page  63. 

4  See  an  article  by  the  author  on  a  New  Excretory  Function  of  the  Liver, 
American  Journal  of  the  Medical  Sciences,  October,  1862. 

6  Ibid. 

6  ROBIN  and  VERDEIL,  Chimie  Anatomique,  tome  ii.,  pp.  480  and  439 


QUANTITATIVE   ANALYSIS.  141 

A  consideration  of  abnormal  or  accidental  constituents  of 
the  blood,  such  as  poisonous  or  medicinal  substances,  does 
not  belong  to  its  physiological  history.  It  is  hardly  necessary 
to  mention  certain  substances,  the  existenc^  of  which  is 
doubtful,  such  as  lactic  acid,  copper,  magnesia,  etc. 


CHAPTEE  III. 

COAGULATION   OF   THE   BLOOD. 

General  considerations — Characters  of  the  clot — Characters  of  the  serum — Coagu- 
lating principle  in  the  blood — Circumstances  which  modify  coagulation — Co- 
agulation of  the  blood  in  the  organism — Spontaneous  arrest  of  hemorrhage — 
Cause  of  coagulation  of  the  blood — Summary  of  the  properties  and  functions 
of  the  blood. 

THE  remarkable  property  in  the  blood  of  spontaneous 
coagulation  has  been  commonly  recognized  as  far  back  as 
we  can  look  into  the  history  of  physiology ;  and  since  the 
immortal  discovery  of  Harvey,  which  naturally  gave  an  im- 
pulse to  investigations  into  the  properties  of  the  circulating 
fluid,  there  have  been  few  subjects  connected  with  the  physi- 
ologj-  of  the  blood  which  have  excited  more  universal  interest. 
At  first,  the  ideas  with  regard  to  the  cause  of  this  phenom- 
enon were  entirely  speculative.  The  first  definite  experi- 
ments on  record  were  performed  by  Malpighi  and  published 
in  1666.  He  was  followed  by  Borelli,  Euysch,  and  a  host  of 
others  who  hold  conspicuous  places  in  the  history  of  our 
science;  among  whom  may  be  mentioned  Hunter,  Hewson, 
Miiller,  Thackrah,  J.  Davy,  Magendie,  Nasse,  and  Dumas. 
While  much  labor  has  been  expended  on  this  subject,  the  final 
cause  of  coagulation  cannot  even  now  be  said  to  be  settled 
beyond  question. 

The  blood  retains  its  fluidity  while  it  remains  in  the 
vessels,  and  circulation  is  not  interfered  with.  It  is  then  co^- 


COAGULATION  OF  THE  BLOOD.  143 

posed,  as  we  have  seen,  of  clear  plasma,  holding  corpuscles  in 
suspension  ;  but  these  little  bodies  do  not  differ  much  from 
the  plasma,  either  in  consistence  or  specific  gravity,  and  give 
to  the  fluid  only  a  slight  degree  of  viscidity.  Shortly  after 
the  circulation  is  interrupted,  or  after  blood  is  drawn  from 
the  vessels,  it  coagulates  or  "  sets"  into  a  jelly-like  mass.  In 
a  few  hours  we  find  that  contraction  has  taken  place,  and  a 
clear,  straw-colored  fluid  has  been  expressed,  the  blood  thus 
separating  into  a  solid  portion,  the  crassamentum  or  clot,  and 
a  liquid,  which  is  called  serum.  The  serum  contains  all  the 
elements  of  the  blood  except  the  red  corpuscles  and  fibrin, 
which  together  form  the  clot.  Coagulation  takes  place  in 
the  blood  of  all  animals,  commencing  a  variable  time  after 
its  removal  from  the  vessels.  In  the  human  subject,  accord- 
ing to  Nasse,1  when  the  blood  is  received  into  a  moderately 
deep,  smooth  vessel,  the  phenomena  of  coagulation  present 
themselves  in  the  following  order  : 

First,  a  gelatinous  pellicle  forms  on  the  surface,  which 
occurs  in  from  1  minute  and  45  seconds  to  6  minutes ; 
in  from  2  to  7  minutes  a  gelatinous  layer  lias  formed 
on  the  sides  of  the  vessel ;  the  whole  mass  becomes  of 
a  jelly-like  consistence  in  from  7  to  16  minutes.  Contrac- 
tion then  begins,  and  if  we  watch  the  surface  of  the  clot  we 
will  see  little  drops  of  clear  serum  making  their  appearance. 
This  fluid  increases  in  quantity,  and  in  from  10  to  12  hours 
separation  is  complete.  The  clot,  which  is  heavier,  sinks  to 
the  bottom  of  the  vessel,  unless  it  contain  bubbles  of  gas,  or 
the  surface  be  very  concave.  In  most  of  the  warm-blooded 
animals  the  blood  coagulates  more  rapidly  than  in  man.  It 
is  particularly  rapid  in  the  class  of  birds,  in  some  of  which 
it  takes  place  almost  instantaneously.  Observations  have 
shown  that  coagulation  is  more  rapid  in  arterial  than  in 
venous  blood.  In  the  former  the  proportion  of  fibrin  is 
notably  greater. 

1  MILNE-EDWARDS,  Lcfons  sur  la  Physiologic,  etc.,  tome  i.,  p.  125. 


144 


THE   BLOOD. 


The  relative  proportions  of  the  serum  and  clot  are  very 
variable,  unless  we  include  in  our  estimate  of  the  serum  that 
portion  which  is  retained  between  the  meshes  of  the  clot.1 
As  the  clot  is  composed  of  corpuscles  and  fibrin,  and  as  these 
in  their  moist  state  represent  in  general  terms  about  one-half 
of  the  blood  (see  table,  page  198),  it  may  be  stated  that  after 
coagulation,  the  actual  proportions  of  the  clot  and  serum 
are  about  equal.  If  we  take  simply  the  serum  which 
separates  spontaneously,  we  have  a  large  quantity  when 
the  clot  is  densely  contracted,  and  a  very  small  quantity  when 
it  is  loose  and  soft.' 


Characters  of  the  Clot. — On  removing  the  clot,  after  the 
separation  of  the  serum  is  complete,  it  presents  a  gelatinous 
consistence,  and  is  more  or  less  firm,  according  to  the  degree 
of  contraction  which  has  taken  place.  As  a  general  rule, 
when  coagulation  lias  been  rapid,  the  clot  is  soft  and  but 
slightly  contracted.  When,  on  the  other  hand,  coagulation 
has  been  slow,  it  contracts  for  a  long  time,  and  is  much 
denser.  When  coagulation  is  slow,  the  clot  frequently  pre- 
sents what  is  known  as  the  cupped  appearance,  having  a  con- 
cave surface,  a  phenomenon  which  merely  depends  on  the 
extent  of  its  contraction.  It  also  presents  a  marked  differ- 

1  It  is  estimated  by  Milne-Edwards  that  the  clot  retains,  in  most  instances, 
one-fifth  of  the  entire  volume  of  serum.  Lemons  sur  la  Physiologic,  etc.,  tome  L, 
p.  124. 

a  According  to  Thackrah  the  following  are  the  periods  required  for  the  coagu- 
lation of  the  blood  in  some  of  the  inferior  animals : 

Horse,  Blood  coagulates  in  from   5  to   13  minutes. 


Ox, 

Dog, 

Sheep, 

Hog, 

Babbit, 

Lamb, 

Duck, 

Fowl, 

Pigeon, 


12 
3 
H 

H 
H 

i 

2 


almost  instantaneously. 


CHAEACTEE8   OF   THE   CLOT.  145 

ence  in  color  at  its  superior  portion.  The  blood  having  re- 
mained fluid  for  some  time,  the  red  corpuscles  settle,  by  virtue 
of  their  greater  weight,  leaving  a  colorless  layer  on  the  top. 
This  is  the  buify  coat  so  frequently  spoken  of  by  authors. 
The  buffed  and  cupped  appearance  of  the  clot  has  been  sup- 
posed to  indicate  an  inflammatory  condition  of  the  circulating 
fluid;  inasmuch  as  the  quantity  of  fibrin  is  generally  in- 
creased in  inflammation,  and  the  greater  the  quantity  of 
fibrin  the  more  rapid  is  the  gravitation  of  the  red  corpuscles. 
Though  this  frequently  presents  itself  in  the  blood  drawn  in 
inflammations,  it  is  by  no  means  pathognomonic  of  this  con- 
dition, and  is  liable  to  occur  whenever  coagulation  is  slow,  or 
retarded  by  artificial  means.  It  is  always  present  in  the 
blood  of  the  horse.  Examined  microscopically,  the  buffy 
coat  presents  fibrils  of  coagulated  fibrin  with  some  of  the 
white  corpuscles  of  the  blood.  On  removing  a  clot  of  ve- 
nous blood  from  the  serum,  the  upper  surface  is  florid  from 
contact  with  the  air,  while  the  rest  of  it  is  dark ;  and  on 
making  a  section,  if  the  coagulation  has  not  been  too  rapid, 
the  gravitation  of  the  red  corpuscles  is  apparent.  The  sec- 
tion, which  is  at  first  almost  black,  soon  becomes  red  from 
contact  with  the  atmosphere.  The  clot  from  arterial  blood 
has  a  dark-red  color.  If  the  clot  be  cut  into  small  pieces,  it 
will  undergo  further  contraction,  and  express  a  part  of  the 
contained  serum.  If  the  clot  be  washed  under  a  stream  of 
water,  at  the  same  time  kneading  it  with  the  fingers,  we  may 
remove  almost  all  the  red  corpuscles,  leaving  the  meshes  of 
fibrin,  which,  on  microscopic  examination,  will  present  the 
fibrillated  appearance  to  which  we  have  already  referred. 
This  is  a  method  sometimes  employed  for  the  extraction  of 
the  fibrin.  It  was  in  this  way  that  fibrin  was  isolated  by 
Malpighi ;  who  made  the  first  experiments  which  rendered 
it  probable  that  coagulation  of  the  blood  depended  upon  this 
principle.  In  a  few  days,  as  the  result  of  putrefaction,  the 
clot  softens,  mixes  with  the  serum,  and  the  blood  regains  its 
fluidity. 

10 


14:6  THE   BLOOD. 

Characters  of  the  Serum. — After  coagulation,  if  the  seruin 
be  carefully  removed,  it  is  found  to  be  a  fluid  of  a  color 
varying  from  a  light  amber  to  quite  a  deep,  but  clear,  red. 
This  depends  upon  a  peculiar  coloring  matter,  distinct  from 
hematine,  but  which  has  never  been  isolated.  The  specific 
gravity  of  the  serum  is  some^diat  less  than  that  of  the  entire 
mass  of  blood;  being,  according  to  Becquerel  and  Rodier, 
about  1,028.'  It  contains  all  the  principles  found  in  the 
plasma,  or  liquor  sanguinis,  with  the  exception  of  the  fibrin. 
It  can  hardly  be  called  a  physiological  fluid,  as  it  is  formed 
only  after  coagulation  of  the  blood,  and  never  exists  isolated 
in  the  body.  The  effusions  which  are  commonly  called 
serum,  though  they  resemble  this  fluid  in  some  particulars, 
are  not  identical  with  it,  being  formed  by  a  process  of  transu- 
dation  rather  than  separation  of  the  blood,  as  in  coagulation. 
"We  have  already  seen  that,  in  the  body,  fibrin  and  albumen 
are  in  combination,  and  that  the  organic  principle  of  the 
serum  (albumen)  when  injected  into  the  vessels  of  a  living 
animal  does  not  become  assimilated,  but  is  rejected  by  the 
kidneys.  The  serum  must  not,  therefore,  be  confounded  with 
the  plasma  or  liquor  sanguinis,  which  is  the  natural  clear 
portion  of  the  blood. 

Coagulating  Principle  in  the  Blood. — Acquainted,  as 
we  are,  with  the  properties  of  fibrin,  it  is  evident  that  this 
principle  is  the  agent  which  produces  coagulation  of  the  blood. 
In  fact,  whatever  coagulates  spontaneously  is  called  fibrin, 
and  whatever  requires  some  agent  to  produce  this  change  of 
consistence  is  called  by  another  name.  But  before  the  prop- 
erties of  fibrin  were  fully  understood,  the  question  of  the 
coagulating  principle  was  a  matter  of  much  discussion.3 
Malpighi  was  probably  the  first  to  isolate  this  principle; 

1  Op.  tit.,  p.  86. 

9  An  admirable  historical  review  of  the  theories  and  discoveries  relating  to 
the  properties  of  fibrin  and  the  coagulation  of  the  blood  is  to  be  found  in  Mr. 
Gulliver's  introduction  to  the  Sydenham  edition  of  the  works  of  William  Hewson, 
London,  1846,  p.  25  el  seq. 


COAGULATING   PRINCIPLE   IN   THE   BLOOD.  14:7 

which  he  did  by  washing  the  clot  in  a  stream  of  water,  which 
removed  the  corpuscles  and  left  a  whitish  fibrous  network. 
His  experiments  are  set  forth  in  an  article  in  which  he  at- 
tempted to  show  that  the  so-called  polypi  of  the  heart  were 
formed  of  fibrin,  though  it  was  not  then  called  by  that  name. 
These  observations  were  soon  confirmed  by  others,  and  finally 
Ruysch  extracted  fibrin  from  his  own  blood  and  the  blood 
of  the  pig  by  whipping  with  a  bundle  of  twigs,  and  thereby 
prevented  its  coagulation.  This  is  the  method  now  most  com- 
monly employed  for  the  separation  of  fibrin.  It  then  became  a 
question  whether  this  substance  existed  as  a  fluid  in  the>  liquor 
sanguinis,  or  was  furnished  by  the  corpuscles  after  the  re- 
moval of  blood  from  the  vessels.  This  was  decided  by  Hew- 
son,  whose  simple  and  conclusive  experiments,  published  in 
1YY1,  leave  no  doubt  that  coagulation  of  the  blood  is  due  to 
fibrin,  and  that  this  principle  is  entirely  distinct  from,  and 
independent  of,  the  corpuscles.  This  observer,  taking  advan- 
tage of  the  property  possessed  by  certain  saline  substances  of 
preventing  the  coagulation  of  the  blood,  was  the  first  to  sepa- 
rate the  liquor  sanguinis  from  the  corpuscles.  He  mixed 
fresh  blood  with  a  little  sulphate  of  soda,  which  prevented 
coagulation,  and  after  the  mixture  had  been  allowed  to  stand 
for  a  time,  the  corpuscles  gravitated  to  the  bottom  of  the  ves- 
sel. The  clear  fluid  was  then  decanted,  and  diluted  with 
twice  its  quantity  of  water,  when  the  fibrin  became  coagu- 
lated.1 Another  experiment  is  still  more  conclusive ;  and  as 
the  credit  of  having  first  separated  the  corpuscles  from  the 
plasma  and  demonstrated  the  coagulability  of  the  latter  is  by 
some  ascribed  to  Miiller,  we  will  give  it  in  the  author's  own 
words : 

"  Immediately  after  killing  a  dog,  I  tied  up  his  jugular 
veins  near  the  sternum,  and  hung  his  head  over  the  edge  of 
the  table,  so  that  the  parts  of  the  veins  where  the  ligatures 
were  might  be  higher  than  his  head.  I  looked  at  the  veins 

1  The  Works  of  William  Hewson,  F.  R.  S.,  Sydenham  edition,  p.  12. 


148  THE   BLOOD. 

from  time  to  time,  and  observed  that  they  became  trans- 
parent at  their  upper  part,  the  red  particles  subsiding.  I 
then  made  a  ligature  upon  one  vein,  so  as  to  divide  the  trans- 
parent from  the  red  portion  of  the  blood ;  and  opening  the 
vein,  [  let  out  the  transparent  portion,  which  was  still  fluid, 
but  coagulated  soon  after.  On  pressing  this  coagulum,  I 
found  it  contained  a  little  serum.  The  other  vein  I  did  not 
open  till  after  the  blood  was  congealed,  and  then  I  found  the 
upper  part  of  the  coagulum  whitish  like  the  crust  in  pleuritic 
blood." l 

Nothing  could  more  conclusively  demonstrate  that  coag- 
ulation of  the  blood  depends  upon  a  coagulating  principle 
existing  in  the  liquor  sanguinis,  than  this  simple  experiment. 
It  also  beautifully  illustrates  the  formation  of  the  buify-coat. 

The  facts  thus  demonstrated  by  Hewson  were  confirmed 
by  Miiller  in  1832.  He  succeeded  in  separating  the  plasma 
from  the  corpuscles  in  the  blood  of  the  frog  by  simple  filtra- 
tion ;  first  diluting  it  with  a  saccharine  solution.  "The  great 
size  of  the  corpuscles  in  this  animal  prevents  their  passage 
through  a  filter,  and  the  clear  fluid  which  is  thus  separated 
soon  forms  a  colorless  coagulum.2 

From  these  observations  it  is  evident  that  the  coagulation 
of  the  blood  is  due  to  the  presence  of  fibrin  in  the  liquor  san- 
guinis. Coagulation  of  this  principle  first  causes  the  whole 
mass  of  blood  to  assume  a  gelatinous  consistence ;  and  by 
virtue  of  its  contractile  properties  it  soon  expresses  the  serum, 
but  the  red  corpuscles  are  retained.  One  of  the  causes  which 
operate  to  retain  the  corpuscles  in  the  clot  is  the  adhesive 
matter  which  covers  their  surface  after  they  escape  from  the 
vessels,  which  produces  the  arrangement  in  rows  like  piles 
of  coin,  which  we  have  already  noted  under  the  head  of 
microscopic  appearances.  This  undoubtedly  prevents  those 


1  The  Works  of  William  Hewson,  F.  R.  S.,  Sydenham  edition,  p.  32. 
3  J.  MUELLER,  Manuel  de  Physiologic,  trad,  par  Jourdan,  Paris,  1851,  tome  i., 
p.  96. 


CIRCUMSTANCES   WHICH   MODIFY   COAGULATION.  149 

which  are  near  the  surface  from  escaping  from  the  clot  during 
its  contraction. 

Circumstances  which  modify  Coagulation  out  of  the  Body. 

The  conditions  which  modify  coagulation  of  the  blood 
have  been  closely  studied  by  Ilewson,  Davy,  Thackrah,  Robin 
and  Yerdeil,  and  others.  They  are,  in  brief,  the  following : 

Blood  flowing  slowly  from  a  small  orifice  is  more  rapidly 
coagulated  than  when  it  flows  in  a  full  stream  from  a  large 
orifice.  If  it  be  received  into  a  shallow  vessel,  it  coagulates 
much  more  rapidly  than  when  received  into  a  deep  vessel. 
If  the  vessel  be  rough,  coagulation  is  more  rapid  than  if  it 
be  smooth  and  polished.  If  the  blood,  as  it  flows,  be  received 
on  a  cloth  or  a  bundle  of  twigs,  it  coagulates  almost  instan- 
taneously. In  short,  it  appears  that  all  circumstances  which 
favor  exposure  of  the  blood  to  the  air,  hasten  its  coagulation. 
The  blood  will  coagulate  more  rapidly  in  a  vacuum .  than  in 
the  air. 

Coagulation  of  the  blood  is  prevented  by  rapid  freezing, 
but  afterwards  takes  place  when  the  fluid  is  carefully  thaw- 
ed. Between  32°  and  140°  Fahr.,  elevation  of  temperature 
increases  the  rapidity  of  coagulation.1  Experiments  are 
impracticable  above  140°,  as  we  are-  then  likely  to  have 
coagulation  of  the  albumen.  According  to  Hichardson,  agi- 
tation of  the  blood  in  closed  vessels  retards,  and  in  open 
vessels  hastens  coagulation.2 

Yarious  chemical  substances  retard  or  prevent  coagula- 
tion. Among  them  we  may  mention :  solutions  of  potash 
and  of  soda;  carbonate  of  soda;  carbonate  of  ammonia; 
carbonate  of  potash ;  ammonia ;  sulphate  of  soda.  In  the 
menstrual  flow  the  blood  is  kept  fluid  by  mixture  with  the 
abundant  secretions  of  the  vaginal  mucous  membrane. 

1  RICHARDSON,  The  Cause  of  the  Coagulation  of  the  Blood.    Astley  Cooper 
Prize  Essay  for  1856,  p.  140  et  seq. 

2  Ibid.,  p.  228. 


150  THE   BLOOD. 


Coagulation  of  the  Blood  in  the  Organism. 

The  blood  coagulates  in  the  vessels  after  death,  though 
less  rapidly  than  when  removed  from  the  body.  As  a  gen- 
eral proposition  it  may  be  stated  that  this  takes  place  in  from 
twelve  to  twenty-four  hours  after  circulation  has"  ceased. 
Under  these  circumstances  it  is  found  chiefly  in  the  venous 
system,  as  the  arteries  are  generally  emptied  by  post  mortem . 
contraction  of  their  muscular  coat.  Coagula  are  found,  how- 
ever, in  the  left  side  of  the  heart  and  in  the  aorta,  but  they 
are  much  smaller  than  those  found  in  the  right  side  of  the 
heart  and  the  large  veins.  These  coagula  present  the  general 
characters  we  have  already  described.  They  are  frequently 
covered  by  a  soft  whitish  film,  analogous  to  the  buffy  coat, 
and  are  dark  in  their  interior. 

It  was  supposed  by  John  Hunter  that  coagulation  of  the 
blood  did  not  take  place  in  animals  killed  by  ]ightning} 
hydrocyanic  acid,  or  prolonged  muscular  exertion,  as  when 
hunted  to  death ;  but  it  appears  from  the  observations 
of  others  that  this  view  is  not  correct.  J.  Davy  reports  a 
case  of  death  by  lightning  where  a  loose  coagulum  was  found 
in  the  heart  twenty-four  hours  after.  In  this  case  decompo- 
sition was  very  far  advanced,  and  it  is  probable  that  the 
coagula  had  become  less  firm  from  that  cause.  His  obser- 
vations also  show  that  coagulation  occurs  after  poisoning  by 
hydrocyanic  acid,  and  in  animals  hunted  to  death.1 

Coagulation  in  different  parts  of  the  vascular  system  is 
by  no  means  unusual  during  life.  In  the  heart  we  sometimes 
find  coagula  which  bear  evidence  of  having  existed  for  some 
time  before  death.  These  were  called  polypi  by  some  of  the 
older  writers,  and  are  often  formed  of  fibrin  almost  free  from 
red  corpuscles.  They  generally  occur  when  death  is  very 
gradual,  and  the  circulation  continues  for  some  time  with 

1  DR.  JOHN  DAYY,  Researches  Physiological  and  Anatomical,  vol.  ii.,  p.  70 
si  *e. 


COAGULATION  IN  THE  ORGANISM.  151 

greatly  diminished  activity.  It  is  probable  that  a  small 
coagulum  is  first  formed,  from  which  the  corpuscles  are 
washed  away  by  the  current  of  blood;  that  this  becomes 
larger  by  farther  depositions,  until  we  have  large  vermicular 
masses  of  fibrin,  attached,  in  some  instances,  to  the  chordae 
tendinese.  Clots  formed  in  this  way  may  be  distinguished  from 
those  formed  after  death  by  their  whitish  color,  dense  consist- 
ence, and  the  closeness  with  which  they  adhere  to  the  walls 
of  the  heart.  Cases  have  been  reported  by  Richardson  and 
others,  where  concretions  of  this  kind  extended  from  the' 
cavities  of  the  heart  far  into  the  large  vessels.  It  is  also 
stated  by  Richardson1  that  they  sometimes  become  partly 
organized,  and  connected  with  the  tissue  of  the  heart ;  but 
we  have  seen  that  accidental  deposits  of  a  proximate  prin- 
ciple, like  fibrin,  never  become  transformed  into  organized 
structures. 

We  need  only  enumerate  some  of  the  other  circumstances 
under  which  the  blood  coagulates  in  the  vessels,  as  this  sub- 
ject belongs  rather  to  pathology  than  to  physiology.  Coag- 
ulation may  be  said,  in  general  terms,  to  occur  as  a  con- 
dition of  stasis.  When  a  ligature  is  applied  to  an  artery, 
the  vessel  becomes  filled  with  a  coagulum  up  to  the  site  of 
the  first  branch  which  is  given  off,  whatever  be  its  situation. 
In  applying  the  ligature,  the  delicate  inner  coat  is  ruptured, 
and  the  shreds,  which  curl  up  in  the  interior  of  the  vessel, 
soon  become  covered  with  a  layer  of  coagulated  blood,  which 
thickens  until  the  whole  vessel  is  filled.  In  cases  in  which 
the  flow  of  blood  becomes  arrested,  or  very  much  retarded, 
as  in  varicose  veins  of  the  extremities,  the  enlarged  veins  in 
hemorrhoids,  etc.,  these  vessels  may  become  obliterated  by  the 
formation  of  a  clot.  In  some  aneurisms,  the  retardation  of 
the  blood-current  produces  spontaneous  cure  by  the  deposi- 
tion of  successive  layers  of  fibrin  next  the  walls  of  the  dilated 
vessel.  A  knowledge  of  this  fact  has  been  made  use  of  in 
the  treatment  of  aneurism  by  compression  of  the  artery  which 

1  Op,  tit. 


152  THE   BLOOD. 

supplies  it  with  blood.  Many  cases  are  on  record,  where  this 
has  been  continued  for  a  number  of  hours,  and  a  cure 
effected. 

Bodies  projecting  into  the  caliber  of  a  blood-vessel  soon 
become  coated  with  a  layer  of  fibrin.  Rough  concretions 
about  the  orifices  of  the  heart*  frequently  induce  the  depo- 
sition of  little  masses  of  fibrin,  which  sometimes  become 
detached,  and  are  carried  to  various  parts  of  the  circulatory 
system,  as  the  lungs  or  brain,  plugging  up  one  or  more  of  the 
smaller  vessels.  These  masses  have  been  called  by  Yirchow, 
emboli,  and  have  been  traced  by  him,  in  some  instances,  from 
the  heart  to  the  situations  above  mentioned.  The  experiment 
has  been  made  of  passing  a  thread  through  a  small  artery, 
allowing  it  to  remain  for  a  few  hours,  when  it  is  found 
coated  with  a  layer  of  coagulated  fibrin. 

Blood  generally  coagulates  when  it  is  effused  into  the 
areolar  tissue,  or  any  of  the  cavities  of  the  body ;  though, 
effused  into  the  serous  cavities,  the  tunica  vaginalis  for  exam- 
ple, it  has  been  known  to  remain  fluid  for  days  and  even 
weeks,  and  coagulate  when  let  out  by  an  incision.  In  the 
Graafian  follicles,  after  the  discharge  of  the  ovum,  we  gener- 
ally have  the  cavity  filled  with  blood,  which  forms  a  clot, 
and  is  slowly  removed  by  the  process  of  absorption. 

Coagulation  thus  takes  place  in  the  vessels  as  the  result 
of  stasis,  or  very  great  retardation  of  the  circulation,  and  in 
the  tissues  or  cavities  of  the  body,  whenever  it  is  accidentally 
effused.  In  the  latter  case,  it  is  generally  removed  in  the 
course  of  time  by  absorption.  This  takes  place  in  the  fol- 
lowing way :  First,  we  have  disappearance  of  the  red  cor- 
puscles, or  decoloration  of  the  clot,  and  the  fibrin  is  then 
the  only  element  which  remains.  This  becomes  reduced 
from  a  fibrillated  to  a  granular  condition,  softens,  finally  be- 
comes amorphous,  and  is  absorbed;  though  when  the  size 
of  the  clot  is  considerable,  this  may  occupy  weeks,  and  even 
months,  and  may  never  be  completely  effected.  Effused  in 
this  manner,  the  constituents  of  the  blood  act  as  foreign 


SPONTANEOUS   ARREST   OF   HEMORRHAGE.  153 

bodies ;  the  corpuscles  cease  to  be  organized  anatomical 
elements  capable  of  self-regeneration,  break  down,  and  are 
absorbed.  The  fibrin  which  remains  undergoes  the  same 
process ;  the  stages  through  which  it  passes  being  always 
those  of  decay,  and  not  of  development.  In  other  words,  it 
is  incapable  of  organization. 

Office  of  the  Coagulation  of  the  Blood  in  Arresting 
Hemorrhage. — The  property  of  the  blood  under  consideration 
has  a  most  important  office  in  the  arrest  of  hemorrhage. 
The  effect  of  an  absence  or  great  diminution  of  the  coagu- 
lability of  the  circulating  fluid  is  exemplified  in  instances 
of  what  is  called  the  hemorrhagic  diathesis ;  a  condition  in 
which  slight  wounds  are  apt  to  be  followed  by  alarming, 
and  it  may  be  fatal,  hemorrhage.  This  condition  of  the 
blood  is  not  characterized  by  any  symptoms  excepting  the 
obstinate  flow  of  blood  from  slight  wounds,  and  may  con- 
tinue for  years.  In  a  case  which  came  under  the  observation 
of  the  author  a  few  years  since,  excision  of  the  tonsils  was 
followed  by  bleeding,  which  continued  for  several  days,  and 
was  arrested  with  great  difficulty.  On  inquiry  it  was 
ascertained  that  the  patient,  a  young  man  about  twenty 
years  of  age,  in  other  respects  perfectly  healthy,  had  been 
subject  from  early  life  to  persistent  hemorrhage  from  slight 
wounds.  In  reviewing  the  functions  of  fibrin,  we  find  that 
apparently  its  most  important  office  is  in  the  arrest  of  hem- 
orrhage. The  degree  of  coagulability  of  the  blood  depends 
on  the  quantity  of  fibrin,  but  its  proportion  has  not  been 
shown  to  bear  any  definite  relation  to  the  vigor  of  the  indi- 
vidual, nor  to  the  processes  of  nutrition  generally.  The 
necessary  and  constant  variations  in  the  organic  elements  of 
the  blood,  which  are  the  result  of  insufficient  alimentation, 
exhausting  discharges,  or  diseases  characterized  by  impover- 
ishment of  this  fluid,  are  observed  in  the  albumen  and  red 
corpuscles,  and  not  in  the  fibrin.  By  this  it  must  not  be 
understood  that  the  quantity  of  fibrin  is  not  variable.  'It  has 


154:  THE    BLOOD. 

been  found,  for  example,  by  Andral  and  Gavarret  to  be  pretty 
generally  increased  in  the  phlegm  asise ;  but  it  bears  no  rela- 
tion to  the  richness  of  the  blood.  Its  proportion  is  not  in- 
creased always  in  plethora  and  diminished  in  anemia ;  and 
in  fact  it  has  been  found  by  Nasse  to  be  increased  in  animals 
suffering  from  hunger.1  After  l^emorrhage,  which  diminishes 
the  corpuscles  and  albumen,  the  fibrin  is  generally  increased ; 
so  that  the  fact  of  loss  of  blood,  diminishing  the  force  of  the 
heart  and  increasing  the  tendency  to  coagulation,  has  an  in- 
fluence in  the  arrest  of  the  flow. 

Circumstances  which  accelerate  coagulation  have  a  ten- 
dency to  arrest  hemorrhage.  It  is  well  known  that  exposure 
of  a  bleeding  surface  to  the  air  has  this  effect.  The  way  in 
which  the  vessel  is  divided  has  an  important  influence.  A 
clean  cut  will  bleed  more  freely  than  a  ragged  laceration.  In 
division  of  large  vessels  this  difference  is  sometimes  marked. 
Cases  are  on  record  where  the  arm  has  been  torn  off  at  the 
shoulder-joint,  and  yet  the  hemorrhage  was,  for  a  time,  spon- 
taneously arrested ;  while  we  know  that  division  of  an  artery 
of  smaller  size,  if  it  be  cut  across,  would  be  fatal  if  left  to 
itself.  Under  these  circumstances  the  internal  coat  is  torn  in 
shreds,  which  retract,  their  curled  ends  projecting  into  the 
caliber  of  the  vessel,  and  have  the  same  effect  on  the  coagu- 
lation of  blood  as  a  bundle  of  twigs.  In  laceration  of  such  a 
large  vessel  as  the  axillary  artery,  the  arrest  cannot  be  per- 
manent, for  as  soon  as  the  system  recovers  from  the  shock, 
the  contractions  of  the  heart  will  force  out  the  coagulated 
blood  which  has  closed  the  opening. 

In  our  study  of  the  functions  of  the  body  we  shall  con- 
tinually see  evidences  that  Nature,  not  content  with  simply 
providing  for  the  ordinary  wants  of  the  system,  has  made 
provision  for  extraordinary  occurrences  and  accidents.  A 
striking  example  of  this  is  the  function  of  fibrin.  All  the 
ordinary  operations  of  the  body  go  on  perfectly  well  in  a 

1  KOBIN  and  YERDEIL,  Chimie  Anatomique,  tome  iii.,  p.  205. 


SPONTANEOUS   ARREST  OF   HEMORRHAGE.  155 

person  affected  with  the  hemorrhagic  diathesis,  in  whose  blood 
the  fibrin  is  wanting  ;  and,  as  we  have  already  seen  in  treat- 
ing of  transfusion,  the  vivifying  effects  of  defibrinated  blood 
are  equal  to  those  of  blood  which  contains  all  its  constituents ; 
yet  it  is  provided  that  in  hemorrhage  the  blood  solidifies  and 
closes  the  opening  in  the  vessels,  if  they  be  not  too  large. 
She  often  makes  attempts  to  cure  aneurisms,  or  hemorrhoids, 
by  the  same  process ;  and  hence  does  not  obliterate  the  vessels 
by  an  organized  substance,  which  would  be  capable  of  self- 
regeneration  and  always  remain  as  part  of  the  body,  but 
throws  out  a  temporary  plug,  which  is  destined  to  be  re- 
moved, partially,  if  not  completely,  by  absorption.  The  pro- 
cess of  coagulation  of  the  fibrin  of  the  blood  is  essentially 
different  from  that  of  gradual  effusion  of  plastic  lymph  by 
which  injuries  are  repaired.  Individuals  suffering  under  the 
hemorrhagic  diathesis,  are  not  deprived  of  the  power  of 
repairing  injuries  by  means  of  plastic  exudations  from  the 
blood,  though  the  blood  contains  no  fibrin,  and  hemorrhage 
is  not  arrested  until  the  process  of  repair  has  closed  the 
openings  in  the  vessels,  or  we  have  closed  them  by  the  effect 
of  our  styptics.  We  likewise  see  that  in  the  lower  animals 
who  have  not  the  means  of  artificially  arresting  hemorrhage, 
its  spontaneous  arrest  is  more  effectually  provided  for  by  a 
more  rapid  coagulation  of  the  blood. 

From  the  foregoing  considerations  it  is  evident  that  the 
remarkable  phenomenon  of  coagulation  of  the  blood,  which 
has  so  much  engaged  the  attention  of  physiologists,  has  rather 
a  mechanical  than  a  vital  function ;  for  its  chief  office  is  in  the 
arrest  of  hemorrhage.  Coagulation  never  takes  place  in  the 
organism,  unless  the  blood  be  in  an  abnormal  condition  with 
respect  to  circulation.  Here  its  operations  are  mainly  con- 
servative ;  but  as  almost  all  conservative  processes  are  some- 
times perverted,  clots  in  the  body  may  be  productive  of  injury, 
as  in  the  instances  of  cerebral  apoplexy,  clots  in  the  heart 
occurring  before  death,  the  detachment  of  emboli,  etc. 


156  THE    BLOOD. 

Cause  of  the  Coagulation  of  the  Blood. — Though  the  phe- 
nomena of  coagulation,  and  the  circumstances  which  modify 
it,  especially  as  occurring  in  the  organism,  are  of  more  prac- 
tical importance  than  any  thing  else,  the  study  of  these 
phenomena  naturally  leads  us  to  inquire  into  the  reason  why 
fibrin  thus  changes  its  form.  When  we  say  that  this  prin- 
ciple is  endowed  with  the  property  of  spontaneous  coagula- 
bility, we  do  not  express  what  is  strictly  the  fact.  It  remains 
fluid  until  it  is  placed  in  abnormal  conditions,  when,  without 
the  application  of  heat,  or  any  chemical  reagents,  it  coag- 
ulates ;  but  so  long  as  it  remains  in  the  circulating  blood, 
lymph,  or  chyle,  coagulation  does  not  take  place.  This 
property,  which  has  been  so  long  recognized,  has  been  the 
subject  of  many  speculations  as  to  its  cause,  and  some  experi- 
ments ;  but  until  the  last  few  years  the  experiments  have  done 
nothing  but  familiarize  us  with  the  actual  phenomena  which 
take  place,  and  left  the  cause,  as  before,  entirely  a  matter  of 
speculation.  Under  these  circumstances  it  will  not  be  found 
very  profitable  to  discuss  the  old  theories  on  the  subject. 
Our  object  in  the  historical  review  of  physiological  questions 
is  to  show  the  gradual  development  of  truth,  as  facts  have 
been  accumulated  by  different  observers,  which  those  last  in 
the  field  have  been  able  to  coordinate,  rather  than  to  exhume 
hypotheses  which  have  fallen  before  actual  observation.  On 
no  subject  have  hypotheses  been  more  vague  and  unsatis- 
factory, and  more  readily  disproved  by  experiment,  than 
with  regard  to  the  cause  of  coagulation  of  the  fibrin.  The 
idea  that  exposure  to  the  air  is  the  cause  of  coagulation, 
which  was  held  by  Hewson,  is  disproved  by  the  simple  fact 
that  coagulation  takes  place  in  a  vacuum.  The  vital  theory 
of  Hunter,  which  was  adopted  by  most  physiologists  of  his 
time,  is  too  indefinite  for  discussion  at  the  present  day,  and 
really  expresses  utter  want  of  knowledge  on  the  subject. 
The  theory  that  motion  is  the  cause  of  the  fluidity  of  fibrin 
in  the  body,  is  disproved  by  the  fact  that  violent  agitation  of 
the  blood  out  of  the  body  does  not  prevent  coagulation. 


CAUSE  OF  COAGULATION  OF  THE  BLOOD.        157 

On  the  other  hand,  we  are  not  justified,  with  Eobin  and 
Yerdeil,  in  abandoning  the  subject  with  the  assertion  that 
it  is  "  as  vain  to  seek  after  the  cause  of  this  fact  as  to  inquire 
why  fibrin  exists,  why  sulphate  of  copper  is  blue,  etc." ; ! 
assuming  that  fibrin  coagulates  merely  because  it  has  the 
property  of  coagulation,  as  albumen  is  coagulated  by  heat, 
or  ca seine  by  acetic  acid.  An  extension  of  this  method  in 
physiology  would  put  an  end  to  all  generalization,  restricting 
the  operations  of  the  intellect  to  the  mere  observation  of 
phenomena. 

Circulating  in  the  organism,  the  plasma  contains,  molec- 
ularly  united  with  each  other  and  uniformly  distributed  in 
the  fluid,  fibrin,  albumen,  salts,  and  volatile  substances. 
Albumen  retains  its  fluidity  out  of  the  body,  until  heat  or 
some  coagulating  agent  is  applied ;  but  by  employing  a 
current  of  galvanism,  which  we  know  changes  the  condition 
of  the  inorganic  substances  in  the  serum,  something  is  taken 
away  which  causes  albumen  to  coagulate,  or  which,  when  it 
existed  unchanged,  retained  albumen  in  its  fluid  condition. 
Is  it  not  possible  that  the  blood  while  circulating  may  contain 
a  substance  capable  of  keeping  fibrin  fluid,  the  evolution  of 
which  out  of  the  body  is  the  cause  of  coagulation  ?  We  are 
particularly  led  to  ask  this  question,  as  we  are  acquainted 
with  many  substances  which  possess  this  property  when  added 
to  blood  drawn  from  the  vessels ;  such  as  carbonate  of  soda, 
ammonia,  etc.  This  idea  forms  a  fit  basis  for  experimental 
inquiry,  by  a  study  of  the  substances  evolved  by  the  blood 
during  coagulation  in  the  form  of  vapor.  If  it  be  objected 
that  no  coagulation  takes  place  in  the  vessels,  while  an  op- 
portunity for  volatilization  is  constantly  presented  in  the 
lungs  in  normal  circulation,  it  must  be  remembered  that  the 
blood  is  continually  washing  out,  as  it  were,  in  the  course  of 
circulation,  matters  formed  in  the  various  parts  of  the  organ- 
ism ;  and  substances  which  are  continually  discharged  by  the 
lungs,  skin,  kidneys,  etc.,  are  necessarily  as  continually  taken 

1  ROBIN  ana  VERDEIL,  op.  cit.,  tome  iii.,  p.  210. 


158  THE   BLOOD. 

up  by  the  blood  in  the  system.  From  this  point  of  view  it 
does  not  seem  entirely  unprofitable  to  look  after  the  cause  of 
the  coagulation  of  the  blood.  It  was  with  such  an  idea  as 
this  that  almost  the  first  definite  experiments  which  we  have 
on  the  cause  of  coagulation,  were  performed.  These  consti- 
tute the  basis  of  the  Astley  Cooper  prize  essay  for  1856,  and 
if  they  be  not  sufficient  to  convince  all  physiologists,  must 
be  acknowledged  to  settle  many  points  with  reference  to  the 
question  under  consideration.  Dr.  Richardson  has  here  given 
us  the  only  definite  and  probable  explanation  of  this  phenom- 
enon that  has  ever  been  presented.1 

The  views  of  Richardson,  and  the  experiments  on  which 
they  are  based,  are  briefly  the  following  : 

Taking  as  a  point  of  departure  the  fact,  which,  as  we  have 
already  seen,  is  sufficiently  proven,  that  all  circumstances 
which  facilitate  the  separation  of  volatile  elements  from  the 
blood  hasten  coagulation,  Richardson  attempted  to  show 
that  the  volatile  substances  which  thus  escape,  if  retained,  or 
if  made  to  pass  through  blood,  will  retard  or  arrest  coagulation. 
His  experiments  on  the  prevention  of  exhalation  are  very 
satisfactory.  The  jugular  vein  is  laid  bare ;  a  portion  of  it, 
filled  with  blood,  is  included  between  two  ligatures,  then 
separated  from  the  body  and  drawn  under  mercury  in  a  U 
tube,  the  vein  being  allowed  to  remain  in  the  bend  of  the 
tube  for  from  nine  to  twenty-four  hours.  At  the  end  of  this 
time  it  is  removed,  the  blood  let  out,  and  exposed  to  the  air. 
In  a  number  of  experiments  he  found  the  blood  entirely  fluid 
when  drawn  from  the  vein  immediately  after  removal  from 
beneath  the  mercury,  while  it  coagulated  firmly  in  a  few 
minutes  after  exposure  to  the  air.2  This  simple  experiment 
we  have  repeated  with  the  same  result.  It  shows  conclusively 
that  coagulation  of  the  blood  is  not  a  consequence  of  simple 
rest,  or  lowering  of  temperature,  and  that  it  is  not  kept  fluid 
in  the  organism  by  any  vital  influence. 

1  RICHARDSON,  The  Cause  of  the  Coagulation  of  the  Blood,  London,  1858. 
a  Ibid.,  p.  204  et  seq. 


CAUSE  OF  COAGULATION  OF  THE  BLOOD.        159 

The  next  experiments,  which  bear  directly  on  the  subject 
under  consideration,  were  made  with  reference  to  the  impor- 
tant question,  whether  the  volatile  substances  escaping  from 
coagulating  blood,  if  passed  through  fresh  blood,  would  have 
the  effect  of  retarding  or  preventing  coagulation.  The  ex- 
periments on  this  point  are  likewise  conclusive.  The  appa- 
ratus which  is  used  consists  of  two  wide-mouthed  bottles, 
capable  of  holding  about  two  ounces,  and  a  Wolffe's  bottle 
capable  of  holding  about  three  pounds.  The  small  bot- 
tles, fitted  with  perforated  corks,  are  half  filled,  and  the 
large  bottle  nearly  filled,  with  fresh  blood.  A  tube  con- 
nected with  a  small  bellows  is  introduced  into  one  of  the 
small  bottles,  passing  nearly  to  the  bottom,  while  a  second 
perforation  in  the  cork  is  fitted  with  a  short  tube  which 
simply  allows  the  escape  of  air  or  vapor.  The  latter  is  con- 
nected with  a  tube  passing  nearly  to  the  bottom  of  the  Wolffe's 
bottle  through  one  of  the  necks,  while  the  other  is  fitted  with 
a  short  tube  to  permit  the  escape  of  the  vapor.  The  vapor 
is  then  made  to  pass  through  the  blood  in  the  third  bottle  by 
a  long  tube  reaching  to  the  bottom.  If  air  be  now  gently 
forced  through  the  apparatus  by  the  bellows,  the  vapor  from 
the  mass  of  blood  (about  two  pounds  is  used)  in  the  large 
bottle  will  pass  through  the  third,  which  contains  but  an 
ounce  of  blood.  In  an  experiment  of  this  kind  performed  by 
Richardson,  "  the  blood  through  which  the  air  was  first  passed 
coagulated  in  two  minutes ;  that  in  the  Wolffe's  bottle  coagu- 
lated in  three  minutes ;  while  the  blood  in  the  third  bottle, 
which  for  a  time  received  a  full  charge  of  the  vapor,  retained 
its  red  color  and  its  fluidity  for  eight  minutes  and  a  half;  as 
long,  in  fact,  as  any  vapor  could  be  sent  through  it.  When 
the  vapor  failed,  and  air  only  began  to  circulate,  this  blood 
coagulated  feebly,  the  fibrin  separating  and  floating  on  the 
top."1 

These  experiments  apparently  have  but  one  explanation. 
As  the  blood  when  drawn  from  the  body  may  sometimes  be 

1  Op.  cit.,  p.  268. 


160  THE   BLOOD. 

kept  fluid  by  preventing  the  escape  of  volatile  substances, 
and  the  vapor  of  coagulating  blood  forced  through  another 
specimen  of  blood  prevents  coagulation  so  long  as  it  continues 
to  pass,  something  is  given  oif  from  the  blood  which,  when 
contained  in  this  fluid,  has  the  power  of  retaining  fibrin  in 
its  fluid  state.  Having  gone  tkus  far  in  the  investigation, 
the  next  point  is  to  subject  the  vapor  of  blood  to  analysis, 
and  ascertain,  if  possible,  what  substance  or  substances  it 
contains  which,  when  retained  in  the  blood,  or  introduced, 
have  the  power  of  keeping  it  fluid. 

This  was  the  next  step  in  .Richardson's  investigations. 
He  found  that  blood-vapor  contained,  among  other  things, 
ammonia.  This  lie  detected  by  passing  blood-vapor  through 
hydrochloric  acid  and  afterwards  testing  it  with  the  per- 
chloride  of  platinum,  forming  the  ammonio-chloride  of  plati- 
num. He  also  obtained  crystals  of  the  chloride  of  ammo- 
nium, by  allowing  the  vapor  to  pass  over  a  glass  slide  moist- 
ened with  hydrochloric  acid.  He  demonstrated  in  this  way 
the  presence  of  ammonia  in  the  exhalation  from  the  blood  of 
the  human  subject,  as  well  as  the  inferior  animals.  He  also 
demonstrated  by  numerous  experiments  that  ammonia  mixed 
with  blood,  or  the  vapor  passed  through  it,  will  prevent  coag- 
ulation ;  while  the  passage  of  air  and  the  various  gases  has 
the  effect  of  hastening,  rather  than  retarding  this  process. 
It  was  further  demonstrated  that  ammonia  is  constantly  dis- 
charged by  the  organism,  particularly  by  the  lungs ;  and,  of 
course,  must  be  as  constantly  produced  in  the  tissues,  and 
taken  tip  by  the  blood  in  the  course  of  the  circulation.1 

The  points  above  enumerated  certainly  seem  to  be  ex- 

1  In  the  discussion  of  Richardson's  views,  we  have  attempted  to  connect  the 
great  experimental  links  in  his  chain  of  evidence.  His  admirable  and  laborious 
treatise  contains  details  of  399  experiments ;  and  though  a  summary  is  given  at 
the  end  of  each  chapter,  and  a  summary  at  the  conclusion,  much  labor  is  necessary 
on  the  part  of  the  reader  to  separate  those  which  are  important  from  the  great 
mass  of  minor  facts,  and  appreciate  the  proofs  of  the  doctrines  advanced.  This, 
as  it  seems  to  me,  has  had  the  effect  of  causing  the  views  of  Dr.  Richardson  to 
receive  far  less  attention  at  the  hands  of  physiologists  than  they  really  merit. 


CAUSE  OF  COAGULATION  OF  THE  BLOOD.        161 

perimentally  proven.  The  experiments  cited  show  conclu- 
sively that  as  blood  coagulates,  out  of  the  body,  a  vapor  is 
given  off  which  contains  some  substance  capable  of  preserv- 
ing the  fluidity  of  the  fibrin ;  and  that  ammonia,  which  is  a 
constituent  of  this  vapor,  has  this  property.  But  the  rigid 
requirements  of  our  science  render  it  necessary,  in  order  to 
establish  the  fact  that  the  evolution  of  ammonia  is  the  sole 
and  constant  cause  of  coagulation,  to  show  how  ammonia  is 
given  off  under  all  the  varied  circumstances  under  which 
coagulation  of  the  blood  is  known  to  take  place.  In  other 
words,  it  must  be  demonstrated  that  the  evolution  of  ammo- 
nia in  coagulation  is  not  a  coincidence,  occurring,  it  may  be, 
pretty  generally,  but  a  necessity.  The  fact  that  ammonia 
added  to  blood  prevents  coagulation  is  not  sufficient  evidence 
of  this ;  for,  as  we  have  seen,  other  substances,  such  as  carbon- 
ate of  soda,  have  the  same  effect. 

Are  there  any  circumstances  under  which  coagulation  of 
blood  takes  place,  where  ammonia  is  not,  and  cannot  be, 
given  off?  There  are  observations  which  seem  to  answer 
this  question  in  the  affirmative;  and  it  becomes  necessary 
now  to  carefully  study,  with  reference  to  this  point,  all  the 
varied  conditions  under  which  the  blood  will  coagulate. 

The  view  that  coagulation  of  the  blood  is  due  to  the 
evolution  of  ammonia  explains  perfectly  how  this  process  is 
hastened  by  exposure  to  air,  by  a  moderately  high  tempera- 
ture, by  a  vacuum,  by  the  blood  flowing  slowly  in  a  small 
stream,  and  in  brief,  the  various  circumstances  which  modify 
coagulation  out  of  the  ~body.  Its  evolution  from  the  blood 
by  the  lungs  is  not  incompatible  with  the  fact  of  the  fluidity 
of  the  blood  in  the  body,  for  it  is  taken  up  from  the  tissues 
as  fast  as  it  is  eliminated.  Some  instances,  however,  of 
coagulation  m  the  ~body,  and  some  experiments  on  coagulation 
out  of  the  body,  when,  as  is  thought,  ammonia  is  not  and 
cannot  be  evolved,  seem  opposed  to  the  view  advanced  by 
Richardson. 

It  is  easy  to  understand,  adopting  the  views  of  Eichard- 
11 


162  THE   BLOOD. 

son,  why  the  blood  coagulates  in  the  body  after  death.  Under 
the  circumstances  in  which  it  is  then  placed,  the  escape  of 
volatile  substances,  though  retarded,  is  evidently  not  pre- 
vented. Thus  when  the  body  is  opened  shortly  after  death, 
we  may  find  the  blood  perfectly  fluid,  coagulating,  however, 
shortly  after  it  is  removed  from  the  vessels  and  exposed  to 
the  air.  During  life,  when  circulation  is  arrested  or  much 
retarded,  the  blood  will  coagulate ;  but  here  there  is  the  same 
opportunity  presented  for  the  escape  of  volatile  matter.  As 
ammonia  is  undoubtedly  received  by  the  blood  in  the  course 
of  circulation,  arrest  of  circulation  in  any  part  of  the  vascular 
system  prevents  the  blood  therein  contained  from  receiving 
its  constant  supply.  As  it  has  been  shown  that  out  of  the 
body  the  evolution  of  ammonia  always  accompanies  coagu- 
lation, we  must  infer  simply  that  coagulation  in  the  body, 
under  the  above-mentioned  circumstances,  is  attended  with 
the  evolution  of  this  principle,  for  the  conditions  here  do  not 
admit  of  direct  experimentation,,  situated  as  the  blood  is  in 
the  midst  of  tissues,  from  which  volatile  substances  are  also 
evolved.  It  is  not  proper,  however,  to  shut  our  eyes  to  the 
fact  that  blood  effused  into  the  tissues  and  into  the  cavities, 
during  life,  has  been  known  to  remain  fluid  for  days  and 
even  weeks,  when  there  are  no  circumstances  which  we  can 
appreciate  as  modifying  or  preventing  the  gradual  evolution 
of  ammonia.  But  we  know  that  there  are  many  animal 
products,  such  as  the  vaginal  mucus,  etc.,  which  prevent 
coagulation ;  and  in  these  instances,  which  are  not  very  fre- 
quent, it  has  not  been  shown  that  some  influence  of  this  kind 
was  not  brought  to  bear  on  the  process.  It  is  a  curious  fact, 
also,  that  leech-drawn  blood  remains  fluid  in  the  body  of  the 
animal.  Richardson  has  verified  this  fact,  but  says  that  he 
can  offer  no  satisfactory  explanation.  He  observed  also  that 
the  blood  flowing  from  the  leech-bite  presented  the  same 
persistent  fluidity,  which  explains  the  well-known  fact  that 
the  insignificant  wound  gives  rise  to  considerable  hemorrhage. 
On.  this  point  he  has  made  the  following  curious  experiment : 


CAUSE  OF  COAGULATION  OF  THE  BLOOD.        163 

"  After  the  leech  was  removed  from  the  arm,  the  wound 
it  had  produced  continued  to  give  out  blood  very  freely.  I 
caught  the  blood  thus  flowing  at  different  intervals,  allowing 
it  to  trickle  into  teaspoons  of  the  same  size  and  shape.  The 
results  were  curious.  The  blood  which  was  received  into  the 
first  spoon,  and  which  was  collected  immediately  after  the 
removal  of  the  leech,  was  dark,  and  showed  the  same  feeble- 
ness of  coagulation  as  the  blood  taken  from  the  leech  itself. 
Another  portion  of  blood,  received  into  a  second  spoon  five 
minutes  later,  coagulated  in  twenty-five  minutes  with  mod- 
erate firmness.  A  third  portion  of  blood,  caught  ten  min- 
utes later  still,  coagulated  in  eight  minutes ;  while  at  the 
end  of  half  an  hour  the  blood  which  still  flowed  from  the 
wound  coagulated  firmly,  and  in  fine  red  clots,  in  two  min- 
utes. Ultimately  the  blood  coagulated  as  it  slowly  oozed 
from  the  wound,  so  that  the  wound  itself  was  sealed  up." 1 

The  existence  of  projections  into  the  caliber  of  vessels, 
or,  as  was  done  by  Simon,  the  passage  of  a  fine  thread  through 
an  artery  or  vein,  will  determine  the  formation  of  a  small 
coagulum  upon  the  foreign  substance,  while  the  circulation 
is  neither  interrupted  nor  retarded.  These  facts  demand 
explanation,  but  all  we  can  say  with  regard  to  them  is,  that 
in  the  present  state  of  our  knowledge  explanation  is  difficult, 
if  not  impossible.  As  before  remarked,  the  process,  under 
these  circumstances,  cannot  be  subjected  to  direct  experiment, 
as  in  the  case  of  the  blood  coagulating  out  of  the  body. 

Since  the  publication  of  Hichardson's  essay,  various 
experiments  on  coagulation  out  of  the  body  have  been  made 
which  are  claimed  to  disprove  his  views.  Dr.  John  Davy 
has  reported  some  experiments  on  the  coagulation  of  blood 
in  the  common  fowl,  in  which  he  attempts  to  show  that  the 
process  is  not  attended  with  the  evolution  of  ammonia,  and 
furthermore,  that  ammonia  mixed  with  the  blood  will  not 
prevent  coagulation.'2  It  is  well  known  that  the  blood  of 

1  Op.  dt.,  p.  207. 

3  JOHN  DAVY,  M.D.,  Physiological  Researches,  London,  1863,  p.  384  et  seq. 


164  THE   BLOOD. 

birds  is  remarkable  for  the  rapidity  of  its  coagulation,  and  is 
therefore  not  so  well  adapted  to  experiments  relative  to  the 
circumstances  which  attend  this  process  as  the  blood  of 
animals  in  which  coagulation  is  less  rapid.  The  experiments 
referred  to  are  imperfect,  and  no  attempt  is  made  to  invali- 
date the  accuracy  of  the  observations  of  Richardson  on  the 
blood  of  mammals  and  the  human  subject 

The  most  recent  experiments  on  this  subject  are  by  Jo- 
seph Lister,  published  in  a  lecture  on  "  Coagulation  of  the 
Blood,"  in  the  u  London  Lancet,"  February,  1864.  The  view 
entertained  by  Mr.  Lister  is,  that  the  blood  is  kept  fluid  in 
the  organism  by  its  contact  with  living  parts ;  and  that  all 
other  contact,  especially  that  of  inorganic  bodies,  produces  a 
tendency  in  this  fluid  to  coagulate.  The  power  of  retaining 
the  fluidity  of  the  blood  he  supposes  to  reside  particularly  in 
the  coats  of  the  blood-vessels,  but  he  further  says :  "  I  think  it 
probable,  though  not  yet  proved,  that  all  living  tissues  have 
these  properties  with  reference  to  the  blood." l  The  ammonia 
theory  he  considers  entirely  fallacious,  and  ascribes  coagula- 
tion either  to  the  contact  of  animal  tissues  after  death,  when 
their  vital  property  of  maintaining  the  fluidity  of  the  blood 
slowly  disappears,  or  the  contact  of  ordinary  matter.2 

Various  experiments  are  cited  in  support  of  the  view  thus 
briefly  given.  In  one  of  them,  the  author,  by  an  ingenious 
mechanism,  draws  the  blood  into  an  apparatus  consisting  of 
a  tube  in  which  it  is  eifectually  secluded  from  the  air,  and 
which  allows  the  fluid  to  be  stirred  with  a  little  wire  which 
is  provided  with  projecting  spokes.  In  one  experiment  the 
tube  was  filled  with  blood,  which  did  not  come  in  contact 
with  the  air,  and  the  blood  stirred  with  the  wire.  In  thirty- 
seven  minutes  the  wire  was  removed  and  found  enveloped  in 
a  mass  of  clot.  In  another  experiment,  "Receiving  blood 
from  the  throat  of  a  bullock  into  two  similar  wide-mouthed 

1  London  Lancet,  American  republication,  Feb.  1864,  p.  91. 

2  This  view,  as  stated  by  Mr.  Lister,  was  entertained  by  Astley  Cooper,  Thack- 
rah,  Briicke,  and  others. 


CAUSE  OF  COAGULATION  OF  THE  BLOOD.         165 

bottles,  I  immediately  stirred  one  of  them  with  a  clean  ivory 
rod  for  ten  seconds  very  gently,  so  as  to  avoid  the  introduc- 
tion of  any  air,  and  then  left  both  undisturbed.  At  the  end 
of  a  certain  number  of  minutes,  I  found  that,  while  the  blood 
which  had  not  been  disturbed  could  be  poured  out  as  a  fluid, 
with  the  exception  of  a  thin  layer  of  clot  on  the  surface  and 
an  incrustation  on  the  interior  of  the  vessel,  the  blood  in  the 
other  vessel,  which  had  been  stirred  for  so  brief  a  period,  was 
already  a  solid  mass." 3 

Other  experiments  are  brought  forward,  modifications  of 
the  one  already  mentioned  as  performed  by  Simon,  showing 
that  incrustations  will  form  on  the  surface  of  foreign  sub- 
stances introduced  into  the  vessels ;  and  that  after  death  their 
introduction  will  induce  coagulation  in  the  entire  vessel  much 
sooner  than  it  would  otherwise  have  taken  place. 

The  idea  of  simple  contact  with  living  tissues  preventing 
coagulation  hardly  merits  discussion.  It  is  well  known  that 
coagulation  frequently  takes  place  during  life,  almost  always 
following  arrest  of  the  circulation.  After  division  of  the  ves- 
sels, the  blood,  in  contact  with  living  parts,  performs  its  con- 
servative function  in  the  arrest  of  hemorrhage.  There  is  cer- 
tainly something  very  curious  in  the  effect  of  the  contact  of 
foreign  substances,  and  the  experiments  on  this  point  are  very 
striking.  Why  is  it  that  a  coagulum  forms  upon  a  fine  thread 
or  a  needle  passed  through  a  vessel ;  or  on  the  wire  with  which 
the  blood  in  Mr.  Lister's  apparatus  was  stirred,  though  there 
was  no  exposure  to  the  air  ?  And  why  did  the  blood,  which 
was  only  gently  stirred  for  a  few  seconds  with  a.  smooth  ivory 
rod,  coagulate  so  much  more  rapidly  than  that  which  was 
undisturbed  ? 

These  are  questions  which  we  must  acknowledge  our 
inability  to  answer.  The  phenomena  cannot  be  satisfactorily 
explained  by  the  supposition  that  ammonia  is  evolved ;  but 
on  the  other  hand,  this  is  not  a  sufficient  reason  for  rejecting 
the  fact,  experimentally  demonstrated,  that,  out  of  the  or- 

1  Op.  cit.,  p.  83. 


166  THE   BLOOD. 

ganism,  ammonia,  a  substance  capable  of  maintaining  the 
fluidity  of  the  fibrin,  is  given  off  from  coagulating  blood. 
We  may  suppose  that  ammonia  separates  itself  from  one 
portion  of  the  blood,  and  is  retained  in  another.  An  experi- 
ment by  Richardson  gives  color  to  this  supposition,  for  in 
one  experiment  011  the  passage  of  blood-vapor  through  blood, 
he  found  that  the  lower  part  coagulated  while  the  upper  part 
remained  fluid;  and  on  examination,  ascertained,  in  expla- 
nation of  this,  that  the  tube  which  carried  the  vapor  into  the 
blood  did  not  extend  to  the  bottom  of  the  vessel.1 

The  effect  of  foreign  bodies  on  coagulation  is  not  more 
inexplicable  than  the  operation  of  inert  substances  in  certain 
chemical  processes ;  as  the  action  of  the  oxide  of  manganese 
in  the  formation  of  oxygen  from  the  chlorate  of  potash ;  or, 
to  take  a  process  more  like  the  one  under  consideration,  the 
formation  of  crystals  on  threads  and  projections  in  vessels,  or 
the  escape  of  electricity  from  points.  Examples  of  this  kind 
in  the  organic  world  are  numerous,  and  we  are  content  to 
say  that  these  facts  are  entirely  beyond  explanation,  in  the 
present  state  of  our  knowledge.  "We  should  hardly  be  sur- 
prised, then,  at  our  inability  to  explain  the  tendency  which 
the  presence  of  foreign  bodies  has  to  induce  the  deposition  of 
so  coagulable  a  substance  as  fibrin.  The  theory  that  coagu- 
lation of  the  blood  is  always,  or  even  generally,  due  to  the 
contact  of  foreign  substances,  or  tissues  which  have  lost  their 
vital  properties  and  act  as  foreign  substances,  must  be  rejected 
as  opposed  to  experiment  and  observation.  When,  as  hap- 
pens in  the  interior  of  the  body,  the  blood  coagulates  under 
circumstances  when  the  process  will  not  admit  of  direct 
experimentation  as  far  as  the  evolution  of  volatile  substances 
is  concerned,  the  best  we  can  do  is  to  apply,  as  far  as  possible, 
the  facts  which  are  proven  with  regard  to  coagulation  out  of 
the  body,  when  the  phenomena  can  be  minutely  studied. 
Here,  at  least  in  the  human  subject  and  in  mammals,  it 
seems  demonstrated  to  be  due  to  the  evolution  of  ammonia. 

1  Op.  cit.,  p.  269. 


SUMMARY   OF   PEOPEETIES   AND  FUNCTIONS.  167 


Summary  of  the  Properties  and  Functions  of  the  Blood. 

The  blood,  constituting  as  nearly  as  can  be  estimated  one- 
eighth  of  the  weight  of  the  body,  is  the  great  nutritive  fluid ; 
its  presence  being  necessary  to  life,  and  its  normal  constitution 
and  circulation  essential  to  the  performance  of  all  the  func- 
tions. 

Anatomically ',  its  most  important  elements  are  a  clear 
plasma  and  the  red  corpuscles,  these  existing  in  about  equal 
proportions.  The  corpuscles  are  intimately  connected  with 
the  function  of  respiration.  Their  chief  office  seems  to  be  to 
carry  oxygen  from  the  lungs  to  the  tissues.  Their  presence 
is  immediately  essential  to  life,  and  their  normal  proportion 
essential  to  health.  They  are  organized  anatomical  elements, 
capable  of  self-regeneration  from  principles  contained  in  the 
plasma.  They  contain  all  the  principles  which  exist  in  the 
plasma,  with  the  difference  that  the  fibrin  and  albumen  of 
the  latter  are  replaced  by  globuline,  and  a  coloring  matter, 
hematine,  is  superadded.  The  plasma  seems  to  be  the  part 
chiefly  employed  in  the  nourishment  of  the  tissues,  some  of 
which,  as  cartilage,  do  not  receive  any  of  the  corpuscular 
elements  of  the  blood. 

Chemically,  the  plasma  contains  all  the  elements  which 
are  necessary  for  the  regeneration  of  all  parts  of  the  body. 
These  are  continually  being  used  up  in  nutrition,  but  are 
replaced  by  the  absorption  of  articles  of  food  after  they  have 
undergone  the  preparation  of  digestion.  In  the  deposition 
of  new  matter  in  the  regeneration  of  the  tissues,  the  organic 
and  inorganic  constituents  of  the  plasma  are  deposited  to- 
gether ;  the  inorganic  elements  of  the  tissues  receiving,  as  it 
were,  the  vital  properties  of  self-regeneration,  which  we  sup- 
pose to  reside  particularly  in  organic  principles,  from  the 
fact  of  their  molecular  union  with  these  organic  principles. 

Of  the  organic  constituents,  albumen  constitutes  by  far 
the  greater  proportion,  and  is  the  one  chiefly  used  in  the- 


168  THE   BLOOD. 

nutrition  of  the  organic  nitrogen ized  elements  of  the  tissues. 
Its  diminution  in  the  blood  to  any  considerable  extent  de- 
termines defective  nutrition.  It  is  proJbable  that  all  the  other 
organic  nitrogenized  principles  are  formed  from  it. 

In  the  blood,  part  of  the  albumen  is  transformed  into 
fibrin,  which  exists  in  small  quantity,  and  does  not  appear 
to  bear  any  relation  to  nutrition.  Its  peculiar  property  of 
spontaneous  coagulation  gives  it  a  most  important  conser- 
vative function  in  the  arrest  of  hemorrhage.  Ammonia,  which 
is  contained  in  the  blood,  has  the  property  of  maintaining  its 
fluidity ;  but  on  exposure  to  air,  or  in  rupture  of  vessels,  we 
have  an  escape  of  ammonia,  and  the  fibrin  by  its  coagulation 
reduces  the  whole  mass  of  blood  to  a  semi-solid  consistence. 
The  proportion  of  fibrin  in  the  blood  bears  no  relation  to  the 
function  of  nutrition.  Its  occasional  absence  only  induces 
obstinate  hemorrhage  on  the  division  of  vessels,  even  of  very 
small  size. 

Fat,  which  exists  in  small  quantity  in  the  blood,  and  sugar, 
which  exists  only  in  certain  parts  of  the  circulatory  system, 
disappear  .in  the  organism  in  a  way  which  is  not  at  present 
understood.  They  are  concerned  in,  and  necessary  to,  the 
processes  of  nutrition  ;  but  the  exact  nature  of  their  function 
is  unknown. 

The  inorganic  constituents  of  the  body  are  found  in  vary- 
ing proportions  in  the  plasma,  and  have  varied  functions. 
Their  presence  tends  to  preserve  the  proper  constitution  of 
the  corpuscles,  which  are  dissolved  and  lost  in  pure  water. 

The  water  which  does  not  enter  into  the  constitution  of 
the  albumen  and  fibrin  serves  to  hold  the  various  salts  in 
solution,  and  cannot  vary  much  in  quantity  from  a  certain 
standard. 

Some  of  the  inorganic  salts,  the  chlorides  particularly, 
seem  to  regulate,  to  a  certain  extent,  the  processes  of  nutri- 
tion, are  found  most  abundantly  in  the  fluids,  and  apparently 
do  not  form  a  very  essential  portion  of  the  tissues  themselves. 
A  tendency  to  an  excess  in  the  blood  is  relieved  by  discharge 


SUMMARY   OF  PROPERTIES   AND  FUNCTIONS.  169 

from  the  system,  and  a  diminution  is  accompanied  by  certain 
indefinite  disorders  in  the  general  processes  of  nutrition. 

The  alkaline  carbonates  have  a  tendency  to  preserve  the 
fluidity  of  the  fibrin. 

Some  of  the  inorganic  salts,  such  as  \ho,  phosphate  of  lime, 
are  important  elements  entering  into  the  constitution  of  the 
various  tissues.  They  are  most  abundant  in  the  solids  and 
semi-solids  of  the  body ;  and  when  their  introduction  with 
food  is  prevented,  we  have  certain  definite  changes  in  the 
constitution  of  some  of  the  tissues,  as  softening  of  the  bones 
in  animals  deprived  of  the  phosphate  of  lime. 

As  already  remarked,  the  inorganic  principles  are  neces- 
sary to,  and  participate  in  the  performance  of  the  vital  func- 
tions of  organic  principles. 

In  addition  to  these  elements,  the  blood  contains  large 
quantities  of  carbonic  acid,  which  is  eliminated  by  the  lungs, 
and  small  quantities  of  other  excrementitious  matters,  such  as 
urea,  the  urates,  cholesterine,  creatine,  creatinine,  and  am- 
monia (which  is  perhaps  an  excretion),  their  proportion  being 
kept  down  by  their  constant  removal  by  the  proper  eliminat- 
ing organs.  Their  increase  in  the  blood  from  any  cause 
produces  toxic  efiects,  which,  as  regards  some,  urea  and  cho- 
lesterine for  example,  are  easily  recognized. 


CHAPTEK  IV. 

CIRCULATION   OF   THE   BLOOD. 

Discovery  of  the  circulation — Physiological  anatomy  of  the  heart — Valves  of  the 
heart — Movements  of  the  heart — Impulse  of  the  heart — Succession  of  move- 
ments of  the  heart — Force  of  the  heart — Action  of  the  valves — Sounds  of  the 
heart — Cause  of  the  sounds  of  the  heart. 

HARVEY  discovered  the  circulation  of  the  blood  in  1616, 
taught  it  in  his  public  lectures  in  1619,  and  in  1628  published 
the  "  Exercitatio  Anatomica  de  Motu  Cordis  et  Sanguinis 
in  Animalibus"  It  is  justly  said  by  Flourens,  in  his  ele- 
gant little  work  on  the  discovery  of  the  circulation,  that 
from  this  discovery  dates  the  epoch  of  modern  physiology, 
when  tradition  began  to  give  place  to  observation.  "When 
we  reflect  that  it  is  through  the  medium  of  the  blood  that 
all  the  processes  of  life  take  place ;  that  all  tissues  are  nour- 
ished by  it,  and  all  fluids  formed  from  it ;  that  it  gives  fresh 
material  to  every  part,  and  takes  away  that  which  is  worn 
out ;  that  it  carries  oxygen  to  every  part  of  the  system,  and 
gives  to  each  structure  its  vital  properties  ;  we  can  form  some 
idea  of  the  state  of  physiology  before  anything  was  known 
of  the  circulation.  This  momentous  discovery,  from  the 
isolated  facts  bearing  upon  it  which  were  observed  by  nu- 
merous anatomists,  to  its  grand  culmination  with  Harvey,  so 
fully  illustrates  the  gradual  development  of  most  great  phy- 
siological truths,  that  it  does  not  seem  out  of  place  to  begin 
our  study  of  the  circulation  with  a  rapid  sketch  of  its  history. 


DISCOVERY   OF  THE   CIRCULATION.  171 

The  facts  bearing  upon  the  circulation  which  were  devel- 
oped before  the  time  of  Harvey  were  chiefly  of  an  anatomical 
character.  Hippocrates  and  his  contemporaries  distinguished 
two  kinds  of  vessels,  arteries  and  veins ;  but  they  regarded 
the  former  as  air-bearing  tubes,  as  their  name  implies,  in 
communication  with  the  trachea.  Galen,  by  a  few  simple 
experiments  upon  living  animals,  demonstrated  the  error  of 
this  view.  He  showed  that  blood  issued  from  divided  arte- 
ries, and  demonstrated  its  presence  in  a  portion  of  one  of 
these  vessels  included  between  two  ligatures  in  a  living  ani- 
mal. His  ideas,  however,  of  the  mode  of  communication 
between  the  arteries  and  veins  were  entirely  erroneous,  be- 
lieving, as  he  did,  in  the  existence  of  numerous  small  orifices 
between  the  ventricles. 

In  1553,  Michael  Servetus,  who  is  generally  regarded  as 
the  discoverer  of  the  passage  of  the  blood  through  the  lungs, 
or  the  pulmonary  circulation,  described  in  "a  work  on  theology 
the  course  of  the  blood  through  the  lungs,  from  the  right  to 
the  left  side  of  the  heart.  This  description,  complete  as  it 
is,  was  merely  incidental  to  the  development  of  a  theory  with 
regard  to  the  formation  of  the  soul,  and  the  development  of 
what  were  called  animal  and  vital  spirits  (spiritus).  The 
same  year,  by  order  of  Calvin,  Servetus  was  burned  alive  at 
Geneva,  and  nearly  every  copy  of  his  work  was  committed  to 
the  flames.  But  one  or  two  copies  of  this  work  are  now  in 
existence.  One  is  in  the  library  of  the  Institute  of  France, 
and  bears  evidence,  in  some  pages  which  are  partially  burned, 
of  the  fate  which  it  so  narrowly  escaped.1 

A  few  years  later,  Columbo,  professor  of  anatomy  at 
Padua,  and  Cesalpinus,  of  Pisa,  also  described  the  passage  of 
the  blood  through  the  lungs,  though  probably  without  any 
knowledge  of  what  had  been  written  by  Servetus.  To  Cesal- 
pinus is  attributed  the  first  use  of  the  expression,  circulation 

1  The  physiological  portion  of  the  Christianismi  Restitutio  of  SERVETUS  has 
been  extracted  from  the  original  by  FLOURENS,  and  is  published  in  his  little  work 
entitled  Histoire  de  la  Decouverte  de  la  Circulation  du  Sang,  Paris,  1854. 


172  CIRCULATION. 

of  the  Uood.  He  also  remarked  that  after  ligature  or  com- 
pression of  veins,  the  swelling  is  always  below  the  point  of 
obstruction.  These  ideas,  the  importance  of  which  is  evi- 
dent now  that  we  understand  the  circulation,  passed  into 
oblivion.  They  were  unknown  to  investigators  during  the 
succeeding  century,  and  were  onljP  brought  to  light  after  the 
discoveries  of  Harvey  had  become  widely  disseminated. 
From  this  point  of  view  they  can  hardly  be  called  discoveries, 
taking  no  place  in  science,  and  their  authors  not  considering 
them  definite  enough,  or  of  sufficient  importance,  to  be  fully 
insisted  upon. 

A  great  discovery,  preparatory  to  that  of  the  circulation, 
was  made  by  Fabricius  ab  Aquapendente,  professor  at  Padua, 
who,  in  the  words  of  Flourens,  had  a  double  glory:  "He 
discovered  the  valves  of  the  veins,  and  he  was  the  master  of 
Harvey."  Yalves  had  been  described  by  Etienne  in  the 
portal  vein,  by  Cananius  in  the  azygos  vein,  and  Eustachi 
had  discovered  the  valve  which  bears  his  name  and  the 
valves  of  the  coronary  veins ;  but  to  Fabricius  is  generally 
ascribed  the  honor  of  the  discovery  of  the  valvular  system  in 
the  veins.1  This  was  demonstrated  to  Harvey  at  Padua, 
though  Fabricius  does  not  appear  to  have  had  any  definite 
idea  of  their  function.  It  is  possible  that  this  anatomical 
fact  may  have  directed  the  mind  of  Harvey  in  his  first  spec- 
ulations on  the  circulation.  Shortly  after  his  return  from 
Padua  in  1602,  he  advanced  beyond  the  study  of  inanimate 
parts  by  dissections,  and  investigated  animated  nature  by 


1  BERARD,  ( Cours  de  Physiologic,  tome  iv.,  p.  34)  quotes  a  passage  from 
Piccolomini,  an  Italian  anatomist,  in  which  the  valves  of  the  veins  are  mentioned : 
"  *-  *  *  quod  est,  in  mediis  venis  reconditas  esse  innumerabiles  pene  valvas, 
quemadmtidum  in  orificiis  vasorum  cordis.  Jfce  venarum  valvce  maxime  con- 
spicuce  sunt  in  divisione  ramorum  vence  cavce"  (Anatomicce  Prcdectiones,  Romce, 
1586,  p.  412).  It  is  the  assertion,  undoubtedly  made  in  good  faith,  in  the  great 
work  of  Fabricius,  that  the  valves  had  never  before  been  seen,  which  has  led  many 
physiologists  to  regard  him  as  the  discoverer ;  especially  when  this  fact  is  taken 
in  connection  with  their  demonstration  by  Fabricius  to  Harvey,  to  whom  is  due 
the  sole  credit  of  having  pointed  out  their  function. 


DISCOVERY   OF   THE    CIRCULATION. 

means  of  vivisections.  As  is  evident  when  we  consider  the 
state  of  science  at  that  time,  anatomists  had  long  been 
preparing  the  way  for  the  discovery  of  the  circulation,  though 
they  knew  little  of  the  functions  of  the  parts  they  described. 
The  conformation  of  the  heart  and  vessels,  and  even  the 
arrangement  of  the  valves  of  the  veins,  did  not  lead  them  to 
suspect  the  course  of  the  blood ;  but  a  few  well  conceived 
experiments  on  living  animals  have  made  it  appear  so  sim- 
ple, that  we  now  wonder  it  remained  unknown  so  long. 
Furthermore,  these  experiments  made  it  evident  that  there 
was  a  communication  at  the  periphery  between  the  arteries 
and  the  veins. 

In  the  work  of  Harvey  are  described,  first,  the  move- 
ments of  the  heart,  which  he  exposed  and  studied  in  living 
animals.  He  describes  minutely  all  the  phenomena  which 
accompany  its  action;  its  diastole,  when  it  is  filled  with 
blood,  and  its  systole,  when  the  fibres  of  which  the  ventricles 
are  composed  contract  simultaneously,  and  "  by  an  admirable 
adjustment  all  the  internal  surfaces  are  drawn  together,  as 
if  with  cords,  and  so  is  the  charge  of  blood  expelled  with 
force."  From  the  description  of  the  action  of  the  ventricles, 
he  passes  to  the  auricles,  and  shows  how  these,  by  their  con- 
m  traction,  fill  the  ventricles  with  blood.  By  experiments 
upon  serpents  and  fishes,  he  proved  that  the  blood,  fills  the 
heart  from  the  veins,  and  is  sent  out  into  the  arteries.  Ex- 
posing the  heart  and  great  vessels  in  these  animals,  he  applied 
a  ligature  to  the  veins,  which  had  the  effect  of  cutting  off 
the  supply  from  the  heart  so  that  it  became  pale  and  flaccid ; 
and  by  removing  the  ligature  the  blood  could  be  seen  flowing 
into  the  organ.  When,  on  the  contrary,  a  ligature  was 
applied  to  the  artery,  the  heart  became  unusually  distended, 
which  continued  as  long  as  the  obstruction  remained.  "When 
the  ligature  was  removed,  the  heart  soon  returned  to  its 
normal  condition.1 

The  descriptions  given  by  Harvey  were  the  result  of  nu- 

1  The  Works  of  William  Harvey,  M.  D.     Sydenham  Edition,  p.  53. 


174:  CIRCULATION. 

merous  experiments  upon  living  animals ;  exposing  the  heart 
of  cold-blooded  animals,  in  which  the  movements  are  com- 
paratively slow;  studying  also  the  action  of  this  organ  in 
warm-blooded  animals,-  after  its  movements  had  become 
enfeebled.  As  we  shall  see  when  we  come  to  describe  the 
movements  of  the  heart,  nothing  can  exceed  the  simplicity 
and  accuracy  of  the  descriptions  of  Harvey,  which  are  uni- 
versally acknowledged  to  be  correct  in  almost  every  par- 
ticular. 

Harvey  completed  his  description  of  the  circulation,  by 
experiments  showing  the  course  of  the  blood  in  the  arteries 
and  veins,  and  the  uses  of  the  valves  of  the  veins.  These 
experiments  are  models  of  simplicity  and  pertinence.  First, 
he  showed  that  a  ligature  tightly  applied  to  a  limb  prevented 
the  blood  from  entering  the  artery  and  arrested  pulsation. 
The  ligature  then  relaxed,  and  applied  with  moderate  tight- 
ness so  as  to  compress  only  the  superficial  veins,  allowed  the 
blood  to  pass  into  the  part  by  the  arteries,  but  prevented  its 
return  by  the  veins,  which  consequently  became  excessively 
congested.  The  ligature  being  removed,  the  veins  soon 
emptied  themselves,  and  the  member  regained  its  ordinary 
appearance.1 

He  observed  the  "  knots"  in  the  veins  of  the  arm  when  a 
ligature  is  applied,  as  for  phlebotomy,  and  showed  that  the 
space  between  these  knots,  which  are  formed  by  the  valves, 
could  be  emptied  of  blood  by  pressing  toward  the  heart,  and 
would  not  fill  itself  while  the  finger  was  kept  at  the  lower 
extremity.  It  was  impossible,  by  pressure  with  the  fingers, 
to  force  the  blood  back  through  one  of  the  valves.3 

By  such  simple,  yet  irresistibly  conclusive  experiments, 
was  completed  the  chain  of  evidence  establishing  the 
fact  of  the  circulation  of  the  blood.  Truly  is  it  said  that 
here  commenced  an  epoch  in  the  study  of  physiology ;  for 
then  the  scientific  world  began  to  emancipate  itself  from  the 
ideas  of  the  ancients,  which  had  held  despotic  sway  for  two 

1  Op.  cit.t  p.  55  et  seq.  9  Ibid.,  p.  65. 


DISCOVERY   OF  THE   CIRCULATION.  175 

centuries,  and  study  Nature  for  themselves  by  means  of 
experiments. 

Though  Harvey  described  so  perfectly  the  course  of  the 
blood,  and  left  not  a  shadow  of  doubt  as  to  the  communica- 
tion between  the  arteries  and  veins,  it  was  left  to  others  to 
actually  see  the  blood  in  movement  and  follow  it  from  one 
system  of  vessels  to  the  other.  In  1661,  Malpighi  saw  the 
blood  circulating  in  the  vessels  of  the  lung  of  a  living  frog, 
in  examining  it  with  magnifying  glasses ;  and  a  little  later, 
Leeuwenhoek  saw  the  circulation  in  the  wing  of  the  bat. 
The  great  discovery  was  then  completed. 

Enough  has  been  said  in  the  preceding  historical  sketch 
to  give  a  general  idea  of  the  course  of  the  great  nutritive 
fluid,  and  the  natural  anatomical  and  physiological  divisions 
of  the  circulatory  system.  There  is  a  constant  flow  from  the 
central  organ  to  all  the  tissues  and  organs  of  the  body,  and  a 
constant  return  of  the  blood  after  it  has  passed  through 
these  parts.  But  before  the  blood,  which  has  thus  been 
brought  back,  is  fit  to  return  again  to  the  system,  it  must  pass 
through  the  lungs  and  undergo  the  changes  which  constitute 
the  process  of  Respiration.  In  some  animals,  like  fishes,  the 
same  force  sends  the  blood  through  the  gills,  and  from  them 
through  the  system.  In  others,  like  the  reptiles,  a  mixture 
of  aerated  and  non-aerated  blood  takes  place  in  the  heart, 
and  the  general  system  never  receives  blood  that  has  been 
fully  arterialized.  But  in  man  and  all  warm-blooded  ani- 
mals, the  organism  demands  blood  that  has  been  fully  purified 
and  oxygenated  by  its  passage  through  the  lungs,  and  here 
we  find  the  first  great  and  complete  divisions  of  the  circula- 
tion into  the  pulmonary  and  systemic,  or,  as  they  have  been 
called,  the  lesser  and  greater  circulation.  The  heart  in  this 
instance  is  double;  having  a  right  and  left  side  which  are 
entirely  distinct  from  each  other.  The  right  heart  receives 
the  blood  as  it  is  brought  from  the  system  by  the  veins,  and 
sends  it  to  the  lungs ;  the  left  heart  receives  the  blood  from 


176  CIECULATIOK". 

the  lungs  and  sends  it  to  the  system.1  It  must  be  borne  in 
mind,  however,  that  though  the  two  sides  of  the  heart  are 
distinct  from  each  other,  their  action  is  simultaneous ;  and  in 
studying  the  motions  of  this  organ,  we  will  find  that  the 
blood  is  sent  simultaneously  from  the  right  side  to  the  lungs, 
and  from  the  left  side  to  the  system*.  It  will  not  be  necessary, 
therefore,  to  separate  the  two  circulations  in  our  study  of 
their  mechanism;  for  the  simultaneous  action  of  both  sides 
of  the  heart  enables  us  to  study  its  functions  as  a  single 
organ,  and  the  constitution  and  operations  of  the  two  kinds 
of  vessels  do  riot  present  any  material  differences. 

For  convenience  of  study,  the  circulatory  system  may  be 
divided  into  heart  and  vessels,  the  latter  being  of  three 
kinds :  the  arteries,  which  carry  blood  from  the  heart  to  the 
system ;  the  capillaries,  which  distribute  the  blood  more  or 
less  abundantly  in  different  parts  of  the  system ;  and  the 
veins,  which  return  the  blood  from  the  system  to  the  heart. 
The  function  of  each  of  these  divisions  may  be  considered 
separately. 

Action  of  the  Heart. 

Physiological  Anatomy  of  the  Heart. — The  heart  of  the 
human  subject  is  a  pear-shaped,  muscular  organ,  situated 
in  the  thoracic  cavity,  with  its  base  about  in  the  median 
line,  and  its  apex  at  the  fifth  intercostal  space,  midway  be- 
tween the  median  line  and  a  perpendicular  dropped  through 
the  left  nipple.  Its  weight  is  from  8  to  10  ounces  in  the 
female,  and  from  10  to  12  ounces  in  the  male.  It  has  four 
distinct  cavities :  a  right  and  a  left  auricle,  and  a  right  and 
a  left  ventricle.  Of  these,  the  ventricles  are  the  more  capa- 
cious. The  heart  is  held  in  place,  or  may  be  said  to  be 
attached,  by  the  great  vessels,  to  the  posterior  wall  of  the 
thorax,  while  the  apex  is  free  and  capable  of  a  certain  degree 

1  In  some  animals,  as  the  dugong,  the  division  between  the  two  sides  of  the 
heart  is  very  marked.  The  heart  is  really  double,  having  two  points,  the  two 
sides  joined  together  only  at  the  base. 


PHYSIOLOGICAL   ANATOMY   OF  THE   HEAKT.  177 

of  motion.     The  whole  organ  is  enveloped  in  a  fibrous  sac 
called  the  pericardium,  lined  by  a  serous  membrane  which  is 
attached  to  the  great  vessels  at  the  base  and  reflected  over  its 
surface.    This  sac  is  lubricated  by  a  drachm  or  two  of  fluid,  so 
that  the  movements  are  normally  accomplished  without  any 
friction.    The  serous  pericardium  does  not  present  any  differ 
ences  from  serous  membranes  in  other  situations.     The  cav 
ities  of  the  heart  are  lined  by  a  smooth  membrane,  called  the 
endocardium,  which  is  continuous  with  the  lining  membrane 
of  the  blood-vessels. 

The  right  auricle  receives  the  blood  from  the  venae  cavse 
and  empties  it  into  the  right  ventricle.  The  auricle  presents 
a  principal  cavity  or  sinus,  as  it  is  called,  with  a  little  appen- 
dix, called,  from  its  resemblance  to  the  ear  of  a  dog,  the 
auricular  appendix.  It  has  two  large  openings  for  the  vena 
cava  ascendens  and  the  vena  cava  descendens,  with  a  small 
opening  for  the  coronary  vein,  which  brings  the  blood  from 
the  substance  of  the  heart  itself.  It  has,  also,  another  large 
opening,  called  the  auriculo-ventricular  opening,  by  which 
the  blood  flows  into  the  ventricle.  The  walls  of  this  cavity 
are  quite  thin  as  compared  with  the  ventricles,  measuring 
about  one  line.  They  are  constituted  of  muscular  fibres 
which  are  arranged  in  two  layers ;  one  of  which,  the  external, 
is  common  to  both  auricles,  and  the  other,  the  internal,  is 
proper  to  each.  These  muscular  fibres,  though  involuntary 
in  their  action,  belong  to  the  striped,  or  what  is  termed  vol- 
untary, variety,  and  are  similar  in  structure  to  the  fibres  of 
the  ventricles.  The  fibres  of  the  auricles  are  much  fewer 
than  those  of  the  ventricles.  Some  of  them  are  looped,  arising 
from  a  cartilaginous  ritfg  which  separates  the  auricles  and 
ventricles,  and  passing  over  the  auricles ;  and  others  are  cir- 
cular, surrounding  the  auricular  appendages  and  the  openings 
of  the  veins,  extending,  also,  a  short  distance  along  the  course 
of  these  vessels.  One  or  two  valvular  folds  are  found  at  the 
orifice  of  the  coronary  vein,  preventing  a  reflux  of  blood ;  but 
there  are  no  valves  at  the  orifices  of  the  venae  cava3. 
12 


178  CIRCULATION. 

The  left  auricle  receives  the  blood  which  comes  from  the 
lungs  by  the  pulmonary  veins.  It  does  not  differ  materially 
in  its  anatomy  from  the  right.  It  is  a  little  smaller,  and  its 
walls  are  thicker,  measuring  about  a  line  and  a  half.  It  has 
four  openings  by  which  it  receives  the  blood  from  the  four  pul- 
monary veins.  These  openings  are  not  provided  with  valves. 
Like  the  right  auricle,  it  has  a  large  opening  by  which  the 
blood  flows  into  the  left  ventricle.  The  arrangement  of  the 
muscular  fibres  is  essentially  the  same  as  in  the  right  auricle. 

In  adult  life  the  cavities  of  the  auricles  are  entirely 
distinct  from  each  other.  Before  birth  they  communicate 
by  a  large  opening,  the  foramen  ovale,  and  the  orifice  of 
the  inferior  vena  cava  is  provided  with  a  membranous  fold, 
the  Eustachian  valve,  which  serves  to  direct  the  blood  from 
the  lower  part  of  the  body  through  this  foramen  into  the 
left  auricle.  After  birth  the  foramen  ovale  is  closed,  and  the 
Eustachian  valve  gradually  disappears. 

The  ventricles,  in  the  human  subject  and  in  warm-blooded 
animals,  constitute  the  bulk  of  the  heart.  They  have  a  ca- 
pacity somewhat  greater  than  that  of  the  auricles,  and  are 
provided  with  thick  muscular  walls.  It  is  by  the  powerful 
action  of  this  portion  of  the  heart  that  the  blood  is  forced,  on 
the  one  hand,  to  the  lungs  and  back  to  the  left  side,  and  on 
the  other,  through  the  entire  system  of  the  greater  circulation 
to  the  right  side.  It  was  supposed  by  Legallois 1  that  the 
capacity  of  the  right  ventricle  was  considerably  greater  than 
the  left,  while  the  more  recent  observations  of  Bouillaud2  on 
the  human  heart  seem  to  show  that  there  is  no  great  differ- 
ence between  the  two  sides  in  this  regard.  The  most  recent 
and  conclusive  observations  on  this  subject  are  those  of  Hif- 
felsheim  and  Robin.3  In  these  experiments  the  cavities 
were  filled  with  an  injection  of  wax,  and  the  estimates 

1  LEGALLOIS,     (Euvres,    Paris,  1824,  tome  i.,  p.  331. 

2  J.  BODILLAUD,  Traitc  Clinique  dcs  Maladies  du  Cceur,  precede  de  Recherches 
nouvelles  sur  V  Anatomic  et  la  Physiologic  de  cette  Organe,  Paris,  1841,  tome  i.,  p.  54. 

3  Journal  de  I1  Anatomic  et  de  la  Physiologic,  Paris,  juillet,  1864,  p.  413. 


PHYSIOLOGICAL   ANATOMY    OF   THE    HEAET.  179 

made  by  calculating  the  amount  of  liquid  displaced  by  the 
moulds  of  the  different  cavities.  Care  was  taken  to  make 
the  injection  in  animals  before  cadaveric  rigidity  set  in,  or 
after  it  had  passed  away  in  the  human  subject.  The  com- 
parative results  obtained  by  these  observers  are  the  most 
interesting,  for  the  cavities  were  undoubtedly  distended  by 
the  injection  to  their  extreme  capacity,  and  contained  more 
than  they  ever  do  during  life.  They  found  the  capacity  of 
the  right  auricle  from  -J¥  to  -|  greater  than  that  of  the  left. 
The  capacity  of  the  right  ventricle  was  from  T1¥  to  ^  greater 
than  that  of  the  left,  but  more  frequently  there  was  less  dis- 
parity between  the  two  ventricles  than  between  the  auricles. 
The  capacity  of  each  ventricle  exceeded  that  of  the  corre- 
sponding auricle  by  from  J  to  -J.  Nine  times  out  of  ten,  this 
predominance  of  the  ventricle  was  more  marked  on  the  left 
side.  The  absolute  capacity  of  the  left  ventricle,  according 
to  these  observations,  is  from  143  to  212  cubic  centimeters, 
which  is  about  4*8  to  7  ounces.  This  is  much  greater  than 
most  estimates,  which  place  the  capacity  of  the  various  cavi- 
ties, moderately  distended,  at  about  2  ounces.  The  estimates 
of  Yolkmann  and  Yalentin  are  about  equal  to  those  we  have 
cited. 

In  spite  of  the  disparity  in  the  extreme  capacity  of  the 
various  cavities,  the  quantity  of  blood  which  enters  the  cav- 
ities is  necessarily  equal  to  that  which  is  expelled.  This. is  given 
in  the  "Cyclopaedia  of  Anatomy  and  Physiology"  (vol.  ii., 
p.  585)  as  a  little  more  than  two  ounces.  There  are  no  means 
of  estimating  with  exactness  the  quantity  of  blood  discharged 
with  each  ventricular  contraction  ;  and  we  find  the  question 
rather  avoided  in  works  on  physiology.  All  we  can  say  is, 
that  from  observation  on  the  heart  during  its  action,  it  never 
seems  to  contain  much  more  than  half  the  quantity  in  all  its 
cavities  that  it  does  when  fully  distended  by  injection ;  but 
it  is  the  right  cavities  which  are  most  dilatable,  and  prob- 
ably the  ordinary  quantity  of  blood  in  the  left  ventricle  is 
within  one-fifth  or  one-sixth  of  its  extreme  capacity. 


180  CIRCULATION. 

The  cavities  of  the  ventricles  are  triangular  or  conoidal ; 
the  right  being  broader  and  shorter  than  the  left,  which  ex- 
tends to  the  apex.  The  inner  surface  of  both  cavities  is 
marked  by  peculiar  ridges  and  papillae,  which  are  called  the 
columnce  carnece.  Some  of  these  are  mere  fleshy  ridges  pro- 
jecting into  the  cavity ;  others  aVe  columns  attached  by  each 
extremity  and  free  at  the  central  portion ;  and  others  are 
papillae  giving  origin  to  the  chordae  tendinece^  which  are  at- 
tached to  the  free  edges  of  the  auriculo-ventricular  valves. 
These  fleshy  columns  interlace  in  every  direction,  and  give 
the  inner  surface  of  the  cavities  a  reticulated  appearance. 
This  arrangement  evidently  facilitates  the  complete  emptying 
of  the  ventricles  during  their  contraction. 

The  walls  of  the  left  ventricle  are  uniformly  much  thicker 
than  the  right.  Bouillaud  found  the  average  thickness  of 
the  right  ventricle  at  the  base  to  be  2J-  lines,  and  the  thick- 
ness of  the  left  ventricle  at  the  corresponding  part  7  lines. 

The  arrangement  of  the  muscular  fibres  constituting  the 
walls  of  the  ventricles  is  more  regular  than  in  the  auricles, 
and  their  course  enables  us  to  explain  some  of  the  phenom- 
ena which  accompany  the  heart's  action.  The  direction  of 
the  fibres  cannot  be  well  made  out  unless  the  heart  has  been 
boiled  for  a  number  of  hours,  when  part  of  the  intermus- 
cular  tissue  is  dissolved  out,  and  the  fibres  can  be  easily  sep- 
arated and  followed.  Without  going  into  a  minute  descrip- 
tion of  their  direction,  it  is  sufficient  to  state,  in  this  con- 
nection, that  they  present  two  principal  layers:  a  super- 
ficial layer  common  to  both  ventricles,  and  a  deep  layer 
proper  to  each.  The  superficial  fibres  pass  obliquely  from 
right  to  left  from  the  base  to  the  apex;  here  they  take  a 
spiral  course,  become  deep,  and  pass  into  the  interior  of  the 
organ  to  form  the  columnse  carnese.  These  fibres  envelop 
both  ventricles.  They  may  be  said  to  arise  from  cartilaginous 
rings  which  surround  the  auriculo-ventricular  orifices.  The 
external  surface  of  the  heart  is  marked  by  a  little  groove 
which  indicates  the  division  between  the  two  ventricles. 


VALVES   OF   THE   HEART. 

The  deep  fibres  are  circular,  or  transverse,  and  surround 
eacli  ventricle  separately. 

The  muscular  tissue  of  the  heart  is  of  a 
deep  red  color,  and  resembles,  in  its  gross 
characters,  the  tissue  of  ordinary  voluntary 
muscles ;  but,  as  already  intimated,  it  pre- 
sents certain  peculiarities  in  its  minute  anat- 
onfy.  The  fibres  are  considerably  smaller 
and  more  granular  than  those  of  ordinary 
muscles.  They  are,  moreover,  connected  with 
each  other  by  short  inosculating  branches, 
while  in  the  voluntary  muscles  each  fibre  runs 

.    .  .       .  •  i  -i    •        Anastomosing:  muscu- 

irom  its  origin  to  its  insertion  enveloped  in  la^  fibres  fro^  the  nu- 

r  man  heart.  (After  Kol- 

its  proper  sheath,  or  sarcolemma.     In  the     ker-> 
heart  the  fibres  have  no  sarcolemma.1     These  peculiarities, 
particularly  the  inosculation  of  the  fibres,  favor  the  contrac- 
tion of  the  ventricular  walls  in  every  direction,  and  the  complete 
expulsion  of  the  contents  of  the  cavities  with  every  systole. 

Each  ventricle  has  two  orifices :  one  by  which  it  receives 
the  blood  from  the  auricle,  and  the  other  by  which  the  blood 
passes  from  the  right  side  to  the  lungs,  and  from  the  left  side 
to  the  system.  All  of  these  openings  are  provided  with  valves, 
which  are  so  arranged  as  to  allow  the  blood  to  pass  in  but 
one  direction. 

Tricuspid  Valve. — This  valve  is  situated  at  the  right 
auriculo-ventricular  opening.  It  has  three  curtains,  formed 
of  a  thin  but  resisting  membrane,  which  are  attached  around 
the  opening.  The  free  borders  are  .attached  to  the  chordae 
tendineae,  some  of  which  arise  from  the  papillae  on  the  inner 
surface  of  the  ventricle,  and  others  directly  from  the  walls  of 

1  ROBIN  states  (Dictionnaire  de  Medecine,  etc.,  de  P.  H.  Nysten,  onzieme  edition 
par  E.  Littre  et  Ch.  Robin.  Coeur.)  that  the  fibres  of  the  heart  have  no  sarco- 
lemma, which  I  believe  to  be  the  fact,  though  Kolliker  (Manual  of  Microscopic 
Anatomy,  London,  1860,  p.  477)  says :  "  Their  sarcolemma  is  very  deh'cate,  or  even 
may  not  be  demonstrable  at  all,  except  by  the  aid  of  reagents." 


182  CIRCULATION. 

the  ventricle.  When  the  organ  is  empty,  these  curtains  are 
applied  to  the  walls  of  the  ventricle,  leaving  the  auriculo- 
ventricular  opening  free ;  but  when  the  ventricle  is  com- 
pletely filled,  and  the  fibres  contract,  they  are  forced  up,  their 
free  edges  become  applied  to  each  other,  and  the  opening  is 
closed. 

Pulmonw  Valves. — These  valves,  also  called  the  semi- 
lunar  or  sigmoid  valves  of  the  right  side,  are  situated  at  the 
orifice  of  the  pulmonary  artery.  They  are  strong  membra- 
nous pouches,  with  their  convexities,  when  closed,  looking 
towards  the  ventricle.  They  are  attached  around  the  orifice 
of  the  pulmonary  artery,  and  are  applied  very  nearly  to  the 
walls  of  the  vessel  when  the  blood  passes  in  from  the  ven- 
tricle ;  but  at  other  times  their  free  edges  meet  in  the  centre, 
forming  an  effectual  barrier  to  regurgitation.  In  the  centre 
of  the  free  edge  of  each  valve  is  a  little  corpuscle  called  the 
corpuscle  of  Arantius  /  and  just  above  these  points  of  attach- 
ment, the  artery  presents  three  little  dilatations,  or  sinuses, 
called  the  sinuses  of  Valsalva.  The  corpuscles  of  Arantius 
have  been  supposed  to  facilitate  the  closure  of  the  valves  by 
slightly  removing  them  from  the  walls  of  the  vessel,  so  that 
the  blood  may  get  behind  them.  This,  however,  is  probably 
not  their  function.  They  aid  in  the  adaptation  of  the  valves 
to  each  other,  and  the  effectual  closure  of  the  orifice. 

Mitral  Valve. — :This  valve,  sometimes  called  the  bicuspid, 
is  situated  at  the  left  auriculo-ventricular  orifice.  It  is  called 
mitral  from  its  resemblance,  when  open,  to  a  bishop's  mitre. 
It  is  attached  to  the  edges  of  the  opening,  and  its  free  borders 
are  held  in  place  when  closed  by  the  chordae  tendinese  of  the 
left  side.  It  presents  no  material  difference  from  the  tri- 
cuspid  valve,  with  the  exception  that  it  is  divided  into  two 
curtains  instead  of  three. 

Aortic  Valves. — These  valves,  also  called  the  semilunar 


MOVEMENTS  OF  THE  HEAKT.  183 

or  sigmoid  valves  of  the  left  side,  present  no  difference  from 
the  valves  at  the  orifice  of  the  pulmonary  artery.  They  are 
situated  at  the  aortic  orifice. 

The  physiological  anatomy  of  the  tricuspid  and  mitral 
valves  may  be  studied,  by  cutting  away  the  auricles  so  as  to 
expose  the  auriculo-ventricular  openings,  introducing  a  pipe 
into  the  pulmonary  artery  and  aorta,  after  destroying  the 
semilunar  valves,  and  then  forcing  water  into  the  ventricles 
by  a  syringe  or  from  a  hydrant.  In  this  way  the  play  of  the 
valves  will  be  beautifully  exhibited. 

We  can  study  the  action  of  the  semilunar  valves,  by 
cutting  away  enough  of  the  ventricles  to  expose  them,  and 
forcing  water  into  the  vessels.  These  experiments  give  an 
idea  of  the  immense  strength  of  the  valves;  for  they  can 
hardly  be  ruptured  by  a  force  which  is  not  sufficient  to  rup- 
ture the  vessels  themselves. 


Movements  of  the  Heart. 

In  studying  the  phenomena  which  accompany  the  action 
of  the  heart,  we  shall  follow  the  course  of  the  blood,  begin- 
ning with  it  as  it  flows  from  the  vessels  into  the  auricles. 
The  dilatation  of  the  cavities  of  the  heart  is  called  the  diastole, 
and  their  contraction  the  systole.  When  these  terms  are 
used  without  any  qualification,  they  are  understood  as  refer- 
ring to  the  ventricles ;  but  they  are  also  applied  to  the  action 
of  the  auricles,  as  the  auricular  diastole  or  systole,  which,  as 
we  shall  see,  is  distinct  from  the  action  of  the  ventricles. 

A  complete  revolution,  so  to  speak,  of  the  heart  consists 
in  the  filling  and  emptying  of  all  its  cavities,  during  which 
they  experience  an  alternation  of  repose  and  activity.  As 
these  phenomena  occupy,  in  many  warm-blooded  animals,-  a 
period  of  time  less  than  one  second,  it  will  be  appreciated 
that  the  most  careful  study  is  necessary  in  order  to  ascertain 
their  exact  relations  to  each  other.  When  the  heart  is  ex- 
posed in  a  living  animal,  the  most  prominent  phenomenon 


184  CIRCULATION. 

is  the  alternate  contraction  and  relaxation  of  the  ventricles ; 
but  this  is  only  one  of  the  operations  of  the  organ.  In  any 
of  the  class  of  mammals  the  anatomy  and  action  of  the  vas- 
cular system  are  to  all  intents  and  purposes  the  same  as  in 
the  human  subject ;  and  though  the  exposure  of  the  heart  by 
opening  the  chest  modifies  somewhat  the  force  and  frequency 
of  its  pulsations,  the  various  phenomena  follow  each  other 
in  their  natural  order,  and  present  essentially  their  normal 
characters.  The  operation  of  exposure  of  the  heart  may  be 
performed  on  a  living  animal  without  any  great  difficulty ; 
and  if  we  simply  take  care  to  keep  up  artificial  respiration, 
the  action  of  the  heart  will  continue  for  a  considerable  time.1 
We  may  keep  the  animal  quiet  by  the  administration  of 
ether,  or  by  poisoning  with  woorara,  the  latter  agent  acting 
upon  the  motor  nerves,  but  having  no  effect  upon  the  heart. 
Having  opened  the  chest,  we  see  the  heart  enveloped  in  its 
pericardium,  regularly  performing  its  functions ;  and  on 
slitting  up  and  removing  this  covering,  the  various  parts  are 
completely  exposed.  The  right  ventricle  and  auricle,  and" 
a  portion  of  the  left  ventricle,  can  be  seen  without  disturbing 
the  position  of  the  parts;  but  the  greater  part  of  the  left 
auricle  is  concealed.  As  both  auricles  and  ventricles  act- 
together,  the  parts  of  the  heart  which  are  exposed  are  suffi- 
cient for  purposes  of  study. 

Action  of  the  Auricles. — Excepting  the  short  time  occu- 
pied in  the  contraction  of  the  auricles,  these  cavities  are  con- 
tinually receiving  blood  on  the  right  side  from  the  system, 
by  the  venae  cavse,  and  on  the  left  side  from  the  lungs,  by 
the  pulmonary  veins.  This  continues  until  their  cavities  are 
completely  filled,  the  blood  coming  in  by  a  steady  current ; 
and  during  the  repose  of  the  heart,  the  blood  is  also  flowing 

1  For  a  full  description  of  the  operations  for  exposing  the  heart  in  living  ani- 
mals, the  reader  is  referred  to  an  article  by  the  author  in  the  American  Journal 
of  the  Medical  Sciences,  October,  1861,  entitled  Experimental  Researches  on  points 
connected  with  the  Action  of  the  Heart  and  with  Respiration. 


MOVEMENTS  OF  THE  HEART.  185 

through  the  patent  auriculo-ventricular  orifices  into  the  ven- 
tricles. When  the  auricles  have  become  fully  distended,  they 
contract  quickly  and  with  considerable  power  ^(the  auricular 
systole),  and  force  the  blood  into  the  ventricles,  effecting  the 
complete  diastole  of  these  cavities.  During  this  contraction, 
the  blood  not  only  ceases  to  flow  in  from  the  veins,  but  some 
of  it  is  regurgitated,  as  the  orifices  by  which  the  vessels  open 
into  the  auricles  are  not  provided  with  valves.  The  size  of 
the  auriculo- ventricular  orifices  is  one  reason  why  the  greater 
portion  of  the  blood  is  made  to  pass  into  the  ventricles ;  and 
furthermore,  during  the  auricular  systole,  the  muscular  fibres 
which  are  arranged  around  the  orifices  of  the  veins  constrict 
them  to  a  certain  extent,  which  tends  to  diminish  the  reflux  of 
blood.  There  can  be  no  doubt  that  some  regurgitation  takes 
place  from  the  auricles  into  the  veins,  but  this  prevents  the 
possibility  of  over-distention  of  the  ventricles. 

It  has  been  shown  by  experiments  that  the  systole  of  the 
auricles  is  not  immediately  necessary  to  the  performance  of 
the  circulation.  M.  Marey,1  in  a  recent  work  on  the  circu- 
lation, cites  an  experiment  of  Chauveau  in  which  the  con- 
tractility of  the  auricles  was  temporarily  exhausted  by  pro- 
longed irritation  ;  nevertheless  the  ventricles  continued  to  act 
and  keep  up  the  circulation. 

Action  of  the  Ventricles. — Immediately  following  the 
contraction  of  the  auricles,  which  has  the  effect  of  producing 
complete  distention  of  the  ventricles,  we  have  the  contraction 
of  the  ventricles.  This  is  the  chief  active  operation  performed 
by  the  heart,  and  is  generally  spoken  of  as  the  systole.  As 
we  should  expect  from  the  great  thickness  of  the  muscular 
walls,  the  contraction  of  the  ventricles  is  very  much  more 
powerful  than  that  of  the  auricles.  By  their  action,  the  blood 
is  forced  from  the  right  side  to  the  lungs  by  the  pulmonary 
artery,  and  from  the  left  side  to  the  system  by  the  aorta. 
Kegurgitation  into  the  auricles  is  effectually  prevented  by  the 

1  MAREY,  Circulation  du  Sang,  Paris,  1863,  p.  36. 


186  CIRCULATION. 

closure  of  the  tricuspid  and  mitral  valves.  This  act  accom- 
plished, the  heart  has  a  period  of  repose,  the  blood  flowing 
into  the  auricles,  and  from  them  into  the  ventricles,  until  the 
auricles  are  filled,  and  another  contraction  takes  place. 

Locomotion  of  the  Heart. — Jhe  position  of  the  heart  after 
death,  or  during  the  repose  of  the  organ,  is  with  its  base  di- 
rected slightly  to  the  right,  and  its  apex  to  the  left  side  of 
the  body ;  but  with  each  ventricular  systole,  it  raises  itself 
up,  the  apex  is  sent  forward,  and  moved  a  little  from  left  to 
right.  The  movement  from  left  to  right  is  a  necessary  con- 
sequence of  the  course  of  the  superficial  fibres.  The  fibres 
on  the  anterior  surface  of  the  organ  are  longer  than  those  on 
the  posterior  surface,  and  pass  from  the  base,  which  is  com- 
paratively fixed,  to  the  apex,  which  is  movable.  From  this 
anatomical  arrangement  the  heart  is  moved  upwards  and 
forwards.  Their  course,  from  the  base  to  the  apex,  is  from 
right  to  left ;  and  as  they  shorten,  the  apex  is  of  necessity 
slightly  moved  from  left  to  right. 

The  locomotion  of  the  entire  heart  forwards  was  observed 
by  Harvey  in  the  case  of  the  son  of  the  Viscount  Montgom- 
ery. "The  young  man,  aged  about  nineteen  years,  suffered  a 
severe  injury  to  the  chest,  resulting  in  an  abscess,  which  on 
cicatrization  left  an  opening  into  which  Harvey  could  intro- 
duce three  fingers  and  the  thumb.  This  opening  was  directly 
over  the  apex  of  the  heart.  The  action  of  the  portion  of  the 
heart  thus  exposed  is  described  by  Harvey  in  the  following 
words : 

"We  also  particularly  observed  the  movements  of  the 
heart,  viz. :  that  in  the  diastole  it  was  retracted  and  with- 
drawn; whilst  in  the  systole  it  emerged  and  protruded; 
and  the  systole  of  the  heart  took  place  at  the  moment  the 
diastole  or  pulse  in  the  wrist  was  perceived.  To  conclude,  the 
heart  struck  the  walls  of  the  chest,  and  became  prominent  at 
the  time  it  bounded  upward  and  underwent  contraction  on 
itself."1 

1  HARVEY,  op.  cit.,  p.  384. 


MOVEMENTS  OF  THE  HEAKT.  187 

The  locomotion  of  the  heart  takes  place  in  the  direction 
of  its  axis,  and  is  due  to  the  sudden  distention  of  the  great 
vessels  at  its  base.  These  vessels  are  eminently  elastic,  and 
as  they  receive  the  charge  of  blood  from  the  ventricles,  be- 
come enlarged  in  every  direction,  and  consequently  project 
the  entire  organ  against  the  walls  of  the  chest.  This 
movement  is  somewhat  aided  by  the  recoil  of  the  ventricles 
as  they  discharge  their  contents.  The  displacement  of  the 
heart  during  its  systole  has  long  been  observed  in  vivisec- 
tions, and  may  be  demonstrated  in  any  of  the  mammals. 
The  most  interesting  observations  on  this  point  are  those  of 
Chauveau  and  Faivre,  which  were  made  upon  a  monkey. 
In  this  animal,  in  which  the  position  of  the  heart  is  very 
much  the  same  as  in  the  human  subject,  the  locomotion  of 
the  organ  was  fully  established.1 

Twisting  of  the  Heart. — The  spiral  course  of  the  super- 
ficial fibres  would  lead  us  to  look  for  another  phenomenon 
accompanying  its  contraction,  namely,  twisting.  If  we 
attentively  watch  the  apex  of  the  heart,  especially  when  its 
action  has  become  a  little  retarded,  there  is  a  palpable  twist- 
ing of  the  point  upon  itself  from  left  to  right  with  the  systole, 
and  an  untwisting  with  the  diastole. 

Hardening  of  the  Heart. — If  the  heart  of  a  living  ani- 
mal be  grasped  by  the  hand,  it  will  be  observed  that  at  each 
systole  it  becomes  hardened.  The  fact  that  it  is  composed 
almost  exclusively  of  fibres  resembling  very  closely  those  of 
the  voluntary  muscles,  explains  this  phenomenon.  Like  any 
other  muscle,  during  contraction  it  is  sensibly  hardened. 

Shortening  and  Elongation  of  the  Heart. — The  foregoing 
phenomena  are  admitted  by  all  writers  on  physiology,  .and 

1  Nbuvelles  Rccherches  experimentales  sur  les  Mouvements  et  les  Bruits  nor- 
maux  du  Coeur,  envisages  au  point  de  vue  de  la  Physiologie  Medicate.  Par  A. 
CHAUVEAU  et  J.  FAIVRE,  Paris,  1856,  p.  24. 


188  CIRCULATION. 

can  easily  be  observed ;  but  the  change  in  length  of  the  heart 
during  its  systole  has  been,  and  is  now,  a  matter  of  discussion. 
All  who  have  studied  the  heart  in  action  have  observed 
changes  in  length  during  contraction  and  relaxation ;  but  the 
contemporaries  of  Harvey  were  divided  as  to  the  periods  in 
the  heart's  action  which  are  Attended  with  elongation  and 
shortening.  Harvey  himself  is  not  absolutely  definite  on  this 
point.  In  one  passage  he  says,  in  describing  the  systole, 
"  that  it  is  everywhere  contracted,  but  especially  towards  the 
sides,  so  that  it  looks  narrower,  relatively  longer ',  more  drawn 
together." '  In  his  description  of  the  case  of  the  Yiscount 
Montgomery,  who  suffered  from  ectopia  cordis,  he  states  that 
during  the  systole,  the  heart  "  emerged  and  protruded."  *  Ye- 
salius,  Riolan,  Fontana,  and  some  others,  contended  for  elon- 
gation during  the  systole;  but  Haller,  Steno,  Lancisi,  and 
Bassuel  contended  that  it  shortened.  The  view  generally 
entertained  at  the  present  day  is  that  the  heart  becomes 
shorter  during  its  systole;  but  there  are  some  eminent  au- 
thorities who  hold  an  opposite  opinion.  Among  the  latter 
may  be  mentioned  Drs.  Pennock  and  Moore,  who  made  a 
great  number  of  experiments  on  the  action  of  the  heart  in 
sheep  and  young  calves.  These  experiments  were  made  in 
Philadelphia  in  1839,  and  it  was  apparently  demonstrated 
that  the  heart  elongated  to  such  a  marked  degree,  that  the 
distance  could  be  measured  with  a  shoemaker's  rule.  In  one 
experiment  (a  ewe  one  year  old),  the  elongation  was  a  quarter 
of  an  inch.3  Of  all  the  writers  of  systematic  works  on  phy- 
siology, Prof.  Dalton  is  the  only  one,  as  far  as  we  know,  who 
accepts  this  view.4  The  experiments  of  this  observer  appa- 


1  HARVEY'S  Works,  published  by  the  Sydenham  Society,  p.  21. 

3  Ibid.,  p.  384. 

8  HOPE,  on  the  Heart.    American  Edition  by  PENNOCK,  Philadelphia,  1846, 
p.  59. 

4  DALTON,  A  Treatise  on  Human  Physiology,  Philadelphia,  1864,  third  edition, 
pp.  275,  276.     The  heart  of  the  eel  is  said  by  Haller  to  elongate  during  its 
ventricular  systole,  though  this  is  denied  by  Fontana  (Memoires  de  Haller*  Lau- 


MOVEMENTS  OF  THE  HEART.  189 

rently  confirm  those  of  Drs.  Pennock  and  Moore.  Some 
experiments  made  by  the  author  a  few  years  ago,  published 
in  the  "American  Journal  of  Medical  Sciences,"  Oct.  1861, 
had  apparently  the  same  result.  There  is  no  doubt  that  the 
point  of  the  heart  is  protruded  during  the  ventricular  systole, 
as  the  experiments  referred  to  conclusively  prove ;  but  the 
author  was  led  by  the  perusal  of  recent  experiments  by  Chau- 
veau  and  Faivre,  to  recognize  the  fact  that  this  protrusion  is 
probably  due  to  other  causes  than  the  elongation  of  the  ven- 
tricles, and  that  during  the  systole  the  ventricles  are  short- 
ened. The  experiment  cited  by  these  eminent  physiologists 
is  very  simple  and  conclusive.  It  is  made  by  suddenly 
cutting  the  heart  out  of  a  warm-blooded  animal,  and  watch- 
ing the  phenomena  which  accompany  the  few  regular  con- 
tractions which  follow.  They  found  that  the  ventricles 
invariably  shortened  during  the  systole.  This  could  easily 
be  appreciated  by  the  eye,  but  more  readily  if  the  point 
of  the  organ  were  brought  just  in  contact  with  a  plane 
surface  at  right  angles,  when  at  each  contraction  it  is 
unmistakably  observed  to  recede.1  This  experiment  we 
have  lately  repeated  before  the  class  of  the  Bellevue  Hos- 
pital Medical  College,  and  have  satisfied  ourselves  of  its 
accuracy.  A  large  Newfoundland  pup,  about  nine  months 
old,  was  poisoned  with  woorara,  artificial  respiration  was 
kept  up,  and  the  heart  exposed.  After  showing  the  protru- 
sion of  the  point  and  the  apparent  elongation  while  in  the 

sanne,  1760,  tome  iii.,  p.  224) ;  but  in  experimenting  on  the  organ  after  excision, 
the  position  in  which  it  is  held  is  important.  If,  for  example,  we  take  the  heart 
of  a  turtle  between  the  thumb  and  finger  and  hold  it  with  the  point  upwards,  the 
ventricle  is  so  thin  and  flabby  that  it  will  become  flattened  during  the  intervals 
of  contraction,  and  the  point  will  be  considerably  elevated  at  each  systole ;  but  if 
we  reverse  the  position  and  allow  the  point  to  hang  down,  it  will  be  drawn  up  and 
the  ventricle  will  shorten  with  the  systole. 

1  CHAUVEAU  ET  FAIVRE,  op.  cit.,  p.  14.  These  observers  show  the  shorten 
ing  of  the  heart  during  its  systole  by  holding  it  by  the  great  vessels  with  the  point 
down.  It  is  more  free  from  sources  of  error  to  observe  the  phenomena  as  the 
heart  lies  on  a  flat  surface. 


190  CIRCULATION. 

chest,  the  organ  was  rapidly  removed,  placed  upon  th£  table, 
and  confined  by  two  long  needles  passed  through  the  base, 
pinning  it  to  the  wood.  It  contracted  for  one  or  two  min- 
utes; and  at  each  systole,  the  ventricles  were  manifestly 
shortened.  The  point  was  then  placed  against  an  upright, 
and  it  receded  with  each  systole  about  an  eighth  of  an  inch. 
This  phenomenon  was  apparent  to  all  present. 

In  another  experiment,  performed  a  few  weeks  later,  the 
heart,  which  had  been  exposed  in  the  same  way,  was  exam- 
ined in  situ  by  pinning  it  with  two  needles  to  a  thin  board 
passed  under  the  organ.  The  presence  of  these  needles  did 
not  seem  to  interfere  with  the  heart's  action,  and  at  each 
ventricular  systole  the  point  evidently  approached  the  base. 
To  render  this  absolutely  certain,  a  knife  was  fixed  in  the 
wood  at  right  angles  to  and  touching  the  point  during  the 
diastole,  and  a  small  silver  tube  was  introduced  through  the 
walls  into  the  left  ventricle.  At  each  contraction,  a  jet  of 
blood  spurted  out  through  the  tube,  and  the  point  of  the  heart 
receded  from  the  knife  about  an  eighth  of  an  inch.  The 
animal  experimented  upon  was  a  dog  a  little  above  the  me- 
dium size. 

These  simple  experiments  demonstrate  that,  in  the  dog 
at  least,  the  ventricles  shorten  during  their  systole.  The 
arrangement  of  the  muscular  fibres  is  too  nearly  identical  in 
the  heart  of  the  warm-blooded  animals  to  leave  room  for 
doubt  that  it  also  shortens  in  the  human  subject. 

The  error  which  has  arisen  in  this  respect,  and  which 
obtained  in  our  former  experiments,  is  due  to  the  locomotion 
and  protrusion  of  the  entire  organ,  so  as  to  make  the  point 
strike  against  the  chest.  A  little  reflection  indicates  the 
mechanism  of  this  phenomenon.  .  During  the  intervals  of 
contraction,  the  great  vessels,  particularly  the  aorta  and  pul- 
monary artery,  which  attach  the  base  of  the  heart  to  the  pos- 
terior wall  of  the  thorax,  are  filled,  but  not  distended,  with 
blood ;  at  each  systole,  however,  these  vessels  are  distended 
to  their  utmost  capacity ;  their  elastic  coats  permit  of  con- 


IMPULSE    OF   THE   HEAKT.  191 

siderable  enlargement,  as  can  be  seen  in  the  living  animal, 
and  this  enlargement,  taking  place  in  every  direction,  pushes 
the  whole  organ  forward.  We  have  also  considerable  loco- 
motion of  the  heart  from  recoil.  It  is  for  this  reason  that, 
observing  the  heart  in  situ,  the  ventricles  seem  to  elongate, 
and  an  instrument  applied  to  it  apparently  indicates  removal 
of  the  apex  from  the  base.  It  is  only  when  we  examine  the 
heart  firmly  fixed,  or  contracting  after  it  is  removed  from  the 
body,  that  we  can  appreciate  the  actual  changes  which  occur 
in  the  length  of  the  ventricles.1 

In  addition  to  these  marked  changes  in  form,  position, 
etc.,  which  the  heart  undergoes  during  its  action,  we  observe, 
on  careful  examination,  that  the  surface  of  the  ventricles 
becomes  marked  with  slight  longitudinal  ridges  during  the 
systole.  This  was  not  observed  by  Harvey,  but  is  men- 
tioned by  Haller.2 

Impulse  of  the  Heart. — Each  movement  of  the  heart  pro- 
duces an  impulse,  which  can  be  readily  felt  and  sometimes 
seen,  in  the  fifth  intercostal  space,  a  little  to  the  left  of  the 
median  line.  Yivisections  have  demonstrated  that  the  impulse 
is  synchronous  with  the  contraction  of  the  ventricles.  If 
the  hand  be  introduced  into  the  chest  of  a  living  animal,  and 
the  finger  placed  between  the  point  of  the  heart  and  the 
walls  of  the  thorax,  every  time  we  have  a  hardening  of  the 
point  the  finger  will  be  pressed  against  the  side.  If  the  im- 
pulse of  the  heart  be  felt  while  the  linger  is  on  the  pulse,  it  is 
evident  that  the  heart  strikes  against  the  thorax  at  the  time  of 
the  distention  of  the  arterial  system.  The  impulse  is  due  to 
the  locomotion  of  the  ventricles.  In  the  words  of  Harvey, 


1  The  observations  of  Fontana  on  the  shortening  of  the  heart  are  very  con- 
clusive. He  constructed  a  little  instrument  consisting  of  two  vertical  rules,  slid- 
ing on  a  horizontal  bar  like  a  shoemaker's  measure,  one  of  which  was  applied  to 
the  base,  and  the  other  just  grazed  the  apex.  He  estimated  the  shortening  of  the 
heart  in  a  lamb  at  about  two  Paris  lines  (Mem.  de  Haller,  tome  iii.,  p.  225). 

a  Elementa  Physiologies,  vol.  i.,  p.  389. 


192  CIRCULATION. 

"  the  heart  is  erected,  and  rises  upwards  to  a  point,  so  that  at 
this  time  it  strikes  against  the  breast  and  the  pulse  is  felt  ex- 
ternally." 1  In  the  case  of  the  son  of  the  Yiscount  Mont- 
gomery, already  referred  to,  Harvey  gives  a  most  graphic  de- 
scription of  the  manner  in  which  the  heart  is  "  retracted  and 
withdrawn  "  during  the  diastole,  and  "  emerged  and  protrud- 
ed "  during  the  systole. 

Succession  of  the  Movements  of  the  Seart. — We  have  al- 
ready followed,  in  a  general  way,  the  course  of  the  blood 
through  the  heart,  and  the  successive  action  of  the  various 
parts ;  but  we  have  yet  to  consider  these  points  more  in  de 
tail,  and  ascertain  if  possible  the  relative  periods  of  activity 
and  repose  in  each  portion  of  the  organ. 

The  great  points  in  the  succession  of  movements  are  read- 
ily observed  in  the  hearts  of  cold-blooded  animals,  where  the 
pulsations  are  very  slow.  In  examining  the  heart  of  the  frog, 
turtle,  or  alligator,  the  alternations  of  repose  and  activity  are 
very  strongly  marked.  During  the  intervals  of  contraction, 
the  whole  heart  is  flaccid,  and  the  ventricle  is  comparative- 
ly pale ;  we  then  see  the  auricles  slowly  filling  with  blood ; 
when  they  have  become  fully  distended,  they  contract  and 
fill  the  ventricle,  which  in  those  animals  is  single ;  the  ven- 
tricle immediately  contracts,  its  action  following  upon  the 
contraction  of  the  auricles  as  if  it  were  propagated  from 
them.  When  the  heart  is  filled  with  blood,  it  has  a  dark  red 
color,  which  contrasts  strongly  with  its  appearance  after  the 
systole.  This  operation  may  occupy  from  ten  to  twenty  sec- 
onds, giving  an  abundance  of  time  for  observation.  The' 
case  is  different,  however,  with  the  warm-blooded  animals,  in 
which  the  anatomy  of  the  heart  is  nearly  the  same  as  in  man. 
Here  a  normal  revolution  may  occupy  less  than  a  second,  and 
it  is  evident  that  the  varied  phenomena  we  have  just  men- 
tioned are  followed  with  the  utmost  difficulty.  In  spite  of 
this  rapidity  of  action,  it  can  be  seen  that  a  rapid  contraction 

1  Op.  dt. 


SUCCESSION   OF   MOVEMENTS    OF   THE   HEAKT.  193 

• 

of  the  auricles  precedes  the  ventricular  systole,  and  that  the 
latter  is  synchronous  with  the  impulse. 

Various  estimates  have  been  made  of  the  relative  time 
occupied  by  the  auricular  and  ventricular  contractions.  This 
interesting  point  has  been  carefully  studied  by  MM.  Chau- 
veau  and  Faivre,  by  auscultating  the  heart  exposed  in  a  living 
animal,  and  establishing,  by  the  touch,  the  relations  between 
the  contractions  of  its  different  parts  and  the  heart  sounds. 
These  observers  made  a  great  number  of  experiments  upon 
horses  and  dogs,  in  which  the  pulse  was  not  more  accelerated 
than  the  pulse  of  the  human  subject.  As  the  result  of  these 
observations,  the  following  numbers  are  given  as  representing 
the  rhythm  of  the  movements  of  the  heart  in  man :  Auricular 
systole,  6 ;  Ventricular  systole,  10 ;  Diastole,  8.1  Though  this 
estimate  is  perhaps  better  than  any  we  had  before,  it  is  evi- 
dent from  the  way  in  which  it  was  arrived  at  that  it  can  be 
nothing  more  than  an  approximation  ;  for  it  is  impossible  to 
estimate  accurately,  by  the  stethoscope  and  the  touch,  opera- 
tions which  follow  each  other  with  such  rapidity. 

This  question  has  been  at  last  definitely  settled  by  the 
late  observations  of  Marey,  who  has  constructed  some  very 
ingenious  instruments  for  registering  the  form  and  frequency 
of  the  pulse.  He  devised  a  series  of  most  interesting  experi- 
ments, in  which  he  was  enabled  to  register  simultaneously 
the  pulsations  of  the  different  divisions  of  the  heart,  and  has 
succeeded  in  establishing  a  definite  relation  between  the  con- 
tractions of  the  auricles  and  ventricles.  The  method  of  M. 
Marey  enables  us  to  determine,  to  a  small  fraction  of  a  sec- 
ond, the  duration  of  the  contraction  of  each  of  the  divisions 
of  the  heart. 

The  method  of  transmitting  the  movement  from  the  heart 
to  a  registering  apparatus  is  very  simple.  It  consists  of  two 
little  elastic  bags  connected  together  by  an  elastic  tube,  the 
whole  closed  and  filled  with  air.  A  pressure,  like  the  pres- 

1  CIIAUVEAU  et  FAIVRE,  op.  tit.,  p.  18.     These  authors  represent  the  rhythm 
by  musical  notes,  which  have  been  reduced  to  the  numbers  given  above. 
13 


194:  CIRCULATION. 

sure  of  the  fingers,  upon  one  of  these  bags  produces,  of  course, 
an  instantaneous  and  corresponding  dilatation  of  the  other.  If 
we  suppose  one  of  these  bags  to  be  introduced  into  one  of  the 
cavities  of  the  heart,  and  the  other  placed  under  a  small  le- 
ver, so  arranged  on  a  pivot  as  to  be  sensible  to  the  slightest 
impression,  it  is  evident  that  a*ny  compression  of  the  bag  in 
the  heart  would  produce  a  corresponding  change  in  volume 
in  the  other,  which  would  be  indicated  by  a  movement  of 
the  lever.  M.  Marey  has  arranged  the  lever  with  its  short 
arm  on  the  elastic  bag,  and  the  long  arm,  provided  with  a 
pen,  moving  against  a  roll  of  paper  which  passes  along  at  a 
uniform  rate.  When  the  lever  is  at  rest  and  the  paper  set 
in  motion,  the  pen  will  make  a  horizontal  mark ;  but  when 
the  lever  ascends  and  descends,  a  corresponding  trace  will  be 
made,  and  the  duration  of  any  movement  can  readily  be  es- 
timated by  calculating  the  rapidity  of  the  motion  of  the 
paper.  The  bag  which  receives  the  impression  is  called  by 
Marey  the  initial  bag,  and  the  other,  which  is  connected  with 
the  lever,  is  called  the  terminal  bag.  The  former  may  be 
modified  in  form  with  reference  to  the  situation  in  which  it 
is  to  be  placed. 

The  experiments  of  M.  Marey,  with  reference  to  the  rela- 
tions between  the  systole  of  the  auricles,  the  systole  of  the 
ventricles,  and  the  impulse  of  the  heart,  were  performed  upon 
horses  in  the  following  way : 

A  sound  is  introduced  into  the  right  side  of  the  heart 
through  the  jugular  vein,  an  operation  which  is  performed 
with  certainty  and  ease.1  This  sound  is  provided  with  two 
initial  bags,  one  of  which  is  lodged  in  the  right  auricle,  while 

1  Catheterization  of  the  cavities  of  the  heart,  especially  upon  the  right  side,  is 
an  operation  familiar  to  physiologists.  With  a  double  canula,  such  as  is  described 
by  Marey  (p.  61),  of  the  requisite  dimensions  and  with  the  proper  curves,  it  must 
be  easy  to  lodge  the  bags  respectively  in  the  auricle  and  ventricle ;  especially  in 
an  animal  of  large  size  like  the  horse.  A  tube  is  easily  introduced  into  the  right 
side  of  the  heart,  in  the  dog,  through  the  external  jugular.  M.  Marey  gives  full 
details  of  every  step  of  the  operation,  and  there  can  be  no  doubt  of  the  facility  and 
accuracy  with  which  it  may  be  performed. 


SUCCESSION   OF   MOVEMENTS   OF   THE   HEART. 


195 


the  other  passes  into  the  ventricle.  The  bags  are  connected 
with  distinct  tubes  which  pass  one  within  the  other,  and  are 
connected  by  elastic  tubing  with  the  registering  apparatus. 
At  each  systole  of  the  heart  the  bags  in  its  cavities  are  com- 
pressed, and  produce  corresponding  movements  of  the  levers, 
which  may  be  registered  simultaneously. 

To  register  the  impulse  of  the  heart,  an  incision-  is  made 
over  the  point  where  the  apex  beat  is  felt,  through  the  skin 

FIG.  2. 


Figure  representing  the  " cardiographe "  of  Marey.  "The  instrument  is  composed 
of  two  principal  elements:  A  E,  the  registering  apparatus,  and  AS,  the  sphygmo- 
graphic  apparatus,  that  is  to  say,  which  receives,  transmits,  and  amplifies  the 
movements  which  are  to  be  studied. "  The  compression  exerted  upon  the  hag  c, 
which  is  placed  over  the  apex  of  the  heart  "between  the  intercostal  muscles,  is  con- 
ducted hy  the  tube  t  c,  which  is  filled  with  air,  to  the  first  lever.  The  compression 
exerted  upon  the  bags  o  and  «,  in  the  double  sound,  is  conducted  by  the  tubes  to 
and  tv  to  the  two  remaining  levers.  The  movements  of  the  levers  are  registered 
simultaneously  by  the  cylinders  AE.  (MAREY,  Sur  la  circulation  du  sang,  Paris, 
1863,  p.  54.)  ' 

and  external  intercostal  muscle.  A  little  bag,  stretched  over 
two  metallic  buttons  separated  by  a  central  rod,  is  then  care- 
fully secured  in  the  cavity  thus  formed,  and  connected  by  an 


196  CIRCULATION. 

elastic  tube  with  the  registering  apparatus.  All  the  tubes 
are  provided  with  stop-cocks,  so  that  each  initial  bag  may  be 
made  to  communicate  with  its  lever  at  will.  "When  the  oper- 
ation is  concluded,  and  the  sound  firmly  secured  in  place  by 
a  ligature  around  the  vein,  the  animal  experiences  no  incon- 
venience, is  able  to  walk  about,  eat,  &c.,  and  there  is  every 
evidence  that  the  circulation  is  not  interfered  with.  The 
cylinders  which  carry  the  paper  destined  to  receive  the  traces 
are  arranged  to  move  by  clock-work  at  a  given  rate.  The 
paper  may  also  be  ruled  in  lines,  the  distances  between  which 
represent  certain  fractions  of  a  second. 

Fig.  2,  taken  from  the  work  of  Marey,  represents  the 
apparatus  reduced  to  one-sixth  of  its  actual  size.  Two  of 
the  levers  are  connected  with  the  double  sound  for  the  right 
auricle  and  ventricle,  and  one  is  connected  with  the  bag  des- 
tined to  receive  the  impulse  of  the  heart. 

In  an  experiment  upon  a  horse,  every  thing  being  care- 
fully arranged  in  the  way  indicated,  the  clock-work  was  set 
in  motion,  and  the  movements  of  the  three  levers  produced 
traces  upon  the  paper  which  were  interpreted  as  follows : 

1.  The  paper  was  ruled  so  that  each  division  represented 
one-tenth  of  a  second.    The  traces  formed  by  the  three  levers 
indicated  four  revolutions  of  the  heart.     The  first  revolution 
occupied  l^  sec.,  the  second  1-^-  sec.,  the  third  1TV  sec.,  and 
the  fourth  1  sec. 

2.  The  auricular  systole,  as  marked  by  the  first  lever, 
immediately  preceded  the  ventricular  systole,  and  occupied 
about  two-tenths  of  a  second.     The  elevation  of  the  lever 
indicated  that  it  was  much  more  feeble  than  ihe  ventricular 
systole,  and  sudden  in  its  character ;  the  contraction,  when 
it  had   arrived   at  the   maximum,  being  immediately  fol- 
lowed by  relaxation. 

3.  The  ventricular  systole,  as  marked  by  the  second  lever, 
followed  immediately  the   auricular   systole,  and  occupied 
about  four-tenths  of  a  second.     The  almost  vertical  direc- 
tion of  the  trace,  and  the  degree  of  elevation,  showed  that  it 


FORCE    OF   THE   HEART.  197 

was  sudden  and  powerful  in  its  character.  The  abrupt  de- 
scent of  the  lever  showed  that  the  relaxation  was  almost  in- 
stantaneous. 

4.  The  impulse  of  the  heart,  as  marked  by  the  third  lever, 
was  shown  to  be  absolutely  synchronous  with  the  ventricular 
systole.1 

Condensing  the  general  results  obtained  by  Marey,  which 
are  of  course  subject  to  a  certain  amount  of  variation,  we 
have,  dividing  the  action  of  the  heart  into  ten  equal  parts, 
three  distinct  periods,  which  occur  in  the  following  order  : 

Auricular  Systole.— -This  occupies  two- tenths  of  the  heart's 
action.  It  is  feeble  compared  with  the  ventricular  systole, 
and  relaxation  immediately  follows  the  contraction. 

Ventricular  Systole. — This  occupies  four-tenths  of  the 
heart's  action.  The  contraction  is  powerful,  and  the  relaxa- 
tion sudden.  It  is  absolutely  synchronous  with  the  impulse 
of  the  heart. 

Diastole. — This  occupies  four-tenths  of  the  heart's  action. 

Force  of  the  Heart. — There  are  few  points  in  physiology 
on  which  opinions  have  been  more  widely  divergent,  than  on 
the  question  of  the  force  employed  by  the  heart  at  each  con- 
traction. Borelli,  who  was  the  first  to  give  a  definite  esti- 
mate of  this  force,  put  it  at  180,000  pounds ;  while  the  calcu- 
lations of  Keill  give  only  5  ounces.2  These  estimates,  how- 
ever, were  made  on  purely  theoretical  grounds.  Borelli  esti- 
mated the  force  employed  by  the  deltoid  in  sustaining  a  given 
weight  held  at  arm's  length,  and  formed  his  estimate  of  the 

1  MAREY,  op.  cit.,  p.  68  et  seq.    I  have  preferred  to  give  the  general  signifi- 
cance of  the  three  traces  obtained  by  Marey,  rather  than  reproduce  the  traces 
themselves,  which  present  certain  minor  characters  which  might  confuse  the  read- 
er.   Nothing  could  be  more  distinct  than  the  illustration  of  the  particular  points 
above  enumerated ;  and  there  can  be  no  other  opinion  than  that  these  observa- 
tions settle  the  question  of  the  rhythm  of  the  heart's  action  in  the  animals  on, 
which  the  experiments  v/ere  performed. 

2  JAMES  KEILL,  M.D.,  Essays  on  Several  Parts  of  the  Animal  (Economy,  Lon- 
don, 1717,  pp.  87,  91. 


198  CIRCULATION. 

power  of  the  heart  by  comparing  the  weight  of  the  organ 
with  that  of  the  deltoid.  Keill  made  his  estimate  from  a 
calculation  of  the  rapidity  of  the  current  of  blood  in  the 
arteries.  Hales  was  the  first  to  investigate  the  question  ex- 
perimentally, by  the  application  of  the  cardiometer.  He 
showed  that  the  pressure  of  blood  in  the  aorta  could  be  meas- 
ured by  the  height  to  which  the  fluid  would  rise  in  a  tube 
connected  with  that  vessel,  and  estimated  the  force  of  the 
left  ventricle  by  multiplying  the  pressure  in  the  aorta  by  the 
area  of  the  internal  surface  of  the  ventricle.  The  cardiometer 
has  undergone  various  improvements  and  modifications,  but 
this  is  the  principle  which  is  so  extensively  made  use  of  at 
the  present  day,  in  estimating  the  pressure  of  the  blood  in 
different  parts  of  the  circulatory  system.  First  we  have  the 
improvement  of  Poiseuille,  who  substituted  a  U  tube  partly 
filled  with  mercury,  for  the  long  straight  tube  of  Hales ;  and 
then  the -various  forms  of  cardiometers  constructed  by  Magen- 
die,  Bernard,  Marey,  and  others,  which  will  be  more  fully 
discussed  in  connection  with  the  arterial  circulation.  These 
instruments  have  been  made  use  of  by  Marey,  with  very 
good  results,  in  investigating  the  relative  force  exerted  by 
the  different  divisions  of  the  heart. 

Hales  estimates,  from  experiments  upon  living  animals, 
the  height  to  which  the  blood  would  rise  in  a  tube  connected 
with  the  aorta  of  the  human  subject,  at  7  feet  6  inches,  and 
gives  the  area  of  the  left  ventricle  as  15  square  inches.  From 
this  he  estimates  the  force  of  the  left  ventricle  at  51*5  pounds.1 

Though  this  estimate  is  only  an  approximation,  it  seems 
based  on  more  reasonable  data  than  any  other. 

The  apparatus  of  Marey  for  registering  the  contrac- 
tions of  the  different  cavities  of  the  heart  enabled  him  to  as- 
certain, also,  the  comparative  force  of  the  two  ventricles  and 
the  right  auricle ;  the  situation  of  the  left  auricle  as  yet  pre- 
cluding the  possibility  of  introducing  a  sound  into  its  cavity. 

1  STEPHEN  HALES,  B.D.,  F.K.S.,  &c.,  Statical  Essays :  Containing  Hwmastaticks, 
&c.,  London,  1733.  Vol.  II.,  p.  40. 


ACTION   OF  THE   VALVES.  199 

By  first  subjecting  the  bags  to  known  degrees  of  pressure, 
the  degree  of  elevation  of  a  lever  may  be  graduated  so  as  to 
represent  the  degrees  of  the  cardiometer.  In  analyzing  traces 
made  by  the  left  ventricle,  right  ventricle,  and  right  auricle, 
in  the  horse,  Marey  found  that,  as  a  general  rule,  the 
comparative  force  of  the  right  and  left  ventricles  is  as  1  to  3.1 
The  force  of  the  right  auricle  is  comparatively  insignifi- 
cant, being  in  one  case,  as  compared  with  the  right*  ventricle, 
only  as  1  to  10. 

Action  of  the  Valves. — "We  have  already  indicated  the 
course  of  the  blood  through  the  cavities  of  the  heart,  and  it 
has  been  apparent  that  the  necessities  of  the  circulation  de- 
mand some  arrangement  by  which  the  current  shall  always 
be  in  one  direction.  The  anatomy  of  the  valves  which  guard 
the  orifices  of  the  ventricles  gives  an  idea  of  their  function ;  but 
we  have  yet  to  consider  the  precise  mechanism  by  which  they 
are  opened  and  closed,  and  the  way  in  which  regurgitation  is 
prevented. 

In  man  and  the  warm-blooded  animals,  there  are  no 
valves  at  the  orifices  by  which  the  veins  open  into  the  auri- 
cles. As  has  already  been  seen,  compared  with  the  ventri- 
cles, the  force  of  the  auricles  is  insignificant ;  and  it  has 
furthermore  been  shown  by  experiment  that  the  ventricles 
may  be  filled  with  blood,  and  the  circulation  continue,  when 
the  auricles  are  entirely  passive.  Though  their  orifices  are 
not  provided  with  valves,  the  circular  arrangement  of  the 
fibres  about  the  veins  is  such,  that  during  the  contraction 
of  the  auricles  the  openings  are  materially  narrowed,  and  re- 
gurgitation  cannot  take  place  to  any  great  extent.  The  force 
of  the  blood  flowing  into  the  auricles  likewise  offers  an  obsta- 
cle to  its  return.  There  is  really  no  valvular  apparatus  which 
operates  to  prevent  regurgitation  from  the  heart  into  the 
veins ;  for  the  valvular  folds  which  are  so  numerous  in  the 

1  MAREY,  op.  cit.,  p.  104. 


200  CIRCULATION. 

general  venous  system,  and  particularly  in  the  veins  of  the 
extremities,  do  not  exist  in  the  vense  cavse. 

The  continuous  flow  of  blood  from  the  veins  into  the 
auricles,  the  feeble  character  of  their  contractions,  the  ar- 
rangement of  the  fibres  around  the  orifices  of  the  vessels,  and 
the  great  size  of  the  auriculo- ventricular  openings,  are  condi- 
tions which  provide  sufficiently  well  for  the  flow  of  blood  into 
the  ventricles. 

Auricula  -  Ventricular  Valves. — After  the  ventricles  have 
become  completely  distended  by  the  auricular  systole,  they 
take  on  their  contraction ;  which,  it  will  be  remembered,  is 
very  many  times  more  powerful  than  the  contraction  of  the 
auricles.  They  have  to  force  open  the  valves  which  close  the 
orifices  of  the  pulmonary  artery  and  aorta,  and  empty  their 
contents  into  these  vessels.  To  accomplish  this,  at  the  moment 
of  the  ventricular  systole,  there  is  an  instantaneous  and  com- 
plete closure  of  the  auriculo-ventricular  valves,  leaving  but 
one  opening  through  which  the  blood  can  pass.  That  these 
valves  close  at  the  moment  of  contraction  of  the  ventricles  is 
demonstrated  by  the  experiments  of  Chauveau  and  Faivre, 
who  introduced  the  finger  through  an  opening  into  the  auri- 
cle, and  actually  felt  the  valves  close  at  the  instant  of  the  ven- 
tricular systole.1 

This  tactile  demonstration,  and  the  fact  that  the  first 
sound  of  the  heart,  which  is  produced  in  great  part  by  the 
closure  of  the  auriculo-ventricular  valves,  is  absolutely  syn- 
chronous with  the  ventricular  systole,  leave  no  doubt  as  to 
the  mechanism  of  the  closure  of  these  valves. 

It  is  probable  that  as  the  blood  flows  into  the  ventricles 
the  valves  are  slightly  floated  out,  but  they  are  not  closed  un- 
til the  ventricles  contract.  A  German  physiologist,  Baum- 
garten,"  has  attempted  to  show  that  the  valves  are  closed  by 
the  contraction  of  the  auricles,  basing  this  opinion  upon  the 
fact  that  when  the  auricles  are  cut  away,  and  fluid  is  poured 

1  Op.  cit.,  p.  21.  a  MILNE-EDWARDS,  op.  cit.,  tome  iv.,  p.  31. 


ACTION   OF   THE   VALVES.  201 

through  the  auriculo-ventricular  opening,  the  valves  are 
floated  up,  and  finally  closed  when  the  ventricle  is  completely 
filled.  This  experiment  we  have  repeated  and  found  to  be 
correct ;  but  in  this  way  we  are  far  from  fulfilling  the  natu- 
ral conditions  of  the  circulation.  In  the  natural  action  of  the 
heart,  the  blood  flows  from  the  auricles  in  a  large  stream, 
which  opens  the  valves  and  applies  them  to  the  walls  of  the 
ventricles.  This  is  quite  different  from  the  action  of  a  small 
stream,  which  may  insinuate  itself  between  the  lips  of  the 
valves,  and  force  them  up  by  reacting  from  the  ventricle.  If 
the  semilunar  valves  be  exposed,  and  the  artery  closed,  a 
stream  of  water  poured  from  the  ventricles  will  close  the 
valves ;  and  yet  we  could  hardly  say  that  in  the  natural  course 
of  the  circulation  the  valves  at  the  arterial  orifices  are  closed 
by  the  ventricular  systole. 

These  experiments  do  not  throw  any  doubt  upon  the  fact 
that  the  auriculo-ventricular  valves  are  closed  by  the  pressure 
of  blood  against  them  during  the  ventricular  systole. 

If  a  bullock's  heart  be  prepared  by  cutting  away  the  auri- 
cles so  as  to  expose  the  mitral  and  tricuspid  valves,  securing 
the  nozzles  of  a  double  syringe  in  the  pulmonary  artery  and 
aorta,  after  having  destroyed  the  semilunar  valves,  and  if 
fluid  be  injected  simultaneously  into  both  ventricles,  the  play 
of  the  valves  will  be  exhibited.  The  mitral  valve  effectually 
prevents  the  passage  of  the  fluid,  its  edges  being  so  accurately 
approximated  that  not  a  drop  passes  between  them ;  but  when 
the  pressure  is  considerable,  a  certain  quantity  of  fluid  passes 
the  tricuspid  valve.  There  is,  indeed,  a  certain  amount  of 
insufficiency  at  the  right  auriculo-ventricular  orifice,  which 
does  not  exist  on  the  opposite  side. 

This  fact  was  first  pointed  out  by  Mr.  T.  W.  King,1  and  is 
called  by  him  the  "  safety-valve  function  of  the  right  ven- 
tride"  The  advantage  of  this  slight  insufficiency  is  apparent 
on  a  little  reflection.  The  right  ventricle  sen  ds  its  blood  to  the 

1  KING,  An  Essay  on  the  Safety-valve  Functions  of  the  Eight  Ventricle  of  the 
Human  Heart. — Guy's  Hospital  Reports,  1837,  vol.  ii.,  p.  104. 


202  CIRCULATION. 

lungs,  where,  in  order  to  facilitate  the  respiratory  processes, 
the  walls  of  the  capillaries  are  very  thin.  The  lungs  them- 
Belves  are  exceedingly  delicate,  and  an  effusion  of  blood,  or 
considerable  congestion,  would  be  liable  to  be  followed  by 
serious  consequences.  To  prevent  this,  the  right  ventricle  is 
not  permitted  to  exert  all  its  "force,  under  all  circumstances, 
upon  the  blood  going  into  the  pulmonary  artery  ;  but  when 
the  action  of  the  heart  is  exaggerated  from  any  cause,  the 
lungs  are  relieved  by  a  slight  regurgitation,  which  takes 
place  through  the  tricuspid  valve.  The  lungs  are  still  further 
protected  by  the  sufficiency  of  the  mitral  valve,  which  pro- 
vides that  no  regurgitation  shall  take  place  into  their  substance 
from  the  left  heart.  In  the  systemic  circulation  the  capilla- 
ries are'less  delicate ;  extravasation  of  blood  would  not  be 
followed  by  any  serious  results,  and  the  circulating  fluid  is 
made  to  pass  through  a  considerable  extent  of  the  elastic 
vessels,  before  it  begins  to  be  distributed  in  the  tissues.  It  is 
evident  that  on  the  left  side  there  is  no  necessity  for  such  a 
provision,  and  it  does  not  exist. 

Aortic  and  Pulmonic  Valves. — The  action  of  the  semi- 
lunar  valves  is  nearly  the  same  upon  both  sides.  In  the  in- 
tervals of  the  ventricular  contractions,  they  are  closed,  and 
prevent  regurgitation  of  blood  into  the  ventricles.  The  sys- 
tole, however,  overcomes  the  resistance  of  these  valves,  and 
forces  the  contents  of  the  ventricles  into  the  arteries.  During 
this  time  the  valves  are  applied,  or  nearly  applied,  to  the 
walls  of  the  vessel ;  but  as  soon  as  the  ventricles  cease  their 
contraction,  the  constant  pressure  of  the  blood,  which,  as  we 
shall  see  hereafter,  is  very  great,  instantaneously  closes  the 
openings. 

The  action  of  the  semilunar  valves  can  be  seen  by  cutting 
away  a  portion  of  the  ventricles  in  the  heart  of  a  large  ani- 
mal, securing  the  nozzles  of  a  double  syringe  in  the  aorta  and 
pulmonary  artery,  and  forcing  water  into  the  vessels.  In 
performing  this  experiment,  it  will  be  noticed  that  while  the 


SOUNDS    OF   THE   HEAKT.  203 

aortic  semilunar  valves  oppose  the  passage  of  the  liquid  so 
effectually  that  the  aorta  may  be  ruptured  before  the  valves 
will  give  way,  a  considerable  degree  of  insufficiency  exists, 
under  a  high  pressure,  at  the  orifice  of  the  pulmonary  artery. 
There  is  at  this  orifice  a  safety-valve  function  as  important 
as  that  ascribed  by  King  to  the  tricuspid  valve.  It  is  evi- 
dent that  the  slight  insufficiency  at  the  pulmonic  orifice  may 
be  even  more  directly  important  in  protecting  the  lungs  than 
the  insufficiency  of  the  tricuspid  valve.  The  difference  in 
the  sufficiency  of  the  semilunar  valves  on  the  two  sides  is 
fully  as  marked  as  between  the  auriculo-ventricular  valves, 
and  it  is  surprising  that  since  the  observations  of  King,  this 
fact  has  not  attracted  the  attention  of  physiologists.1 

It  is  probable  that  the  corpuscles  of  Arantius,  which 
are  situated  in  the  middle  of  each  valvular  curtain,  assist  in 
the  accurate  closure  of  the  orifice.  The  sinuses  of  Yalsalva, 
situated  in  the  artery  behind  the  valves,  are  regarded  as  facil- 
itating the  closure  of  the  valves  by  allowing  the  blood  to  pass 
easily  behind  them. 

Sounds  of  the  Heart. — If  the  ear  be  applied  to  the  prse- 
cordial  region,  it  will  be  found  that  the  action  of  the  heart  is 
accompanied  by  certain  sounds.  A  careful  study  of  these 
sounds,  and  their  modifications  in  disease,  has  enabled  the 
practical  physician  to  distinguish,  to  a  certain  extent,  the 
conditions  of  the  heart.  This  increases  the  purely  physiologi- 
cal interest  which  attaches  to  the  audible  manifestations  of 
the  action  of  the  great  central  organ  of  the  circulation. 

The  appreciable  phenomena  which  attend  the  heart's 
action  are  connected  with  the  systole  of  the  ventricles.  It  is 
this  which  produces  the  impulse  against  the  walls  of  the 
thorax,  and,  as  we  shall  see  further  on,  the  dilatation  of  the 
arterial  system,  called  the  pulse.  It  is  natural,  therefore,  in 

1  This  observation  was  first  made,  and  the  fact  publicly  demonstrated,  in 
the  course  on  physiology  at  the  Bellevue  Hospital  Medical  College,  session  of 
1864-'65. 


204:  CIRCULATION. 

studying  these  phenomena,  to  take  the  systole  as  a  point  of 
departure,  instead  of  the  action  of  the  auricles,  which  we 
cannot  appreciate  without  vivisections ;  and  the  sounds, 
which  are  two  in  number,  have  been  called  first  and  second, 
with  reference  to  the  systole. 

The  first  sound  is  absolutely  synchronous  with  the  apex 
beat.  The  second  sound  follows  the  first  without  any  appre- 
ciable interval.  Between  the  second  and  first  sounds  there 
is  an  interval  of  silence. 

Some  writers  have  attempted  to  represent  the  sounds  of 
the  heart,  and  their  relations  to  each  other,  by  certain  sylla- 
bles, as,  "lull-dup  or  lull-tub  ;"1  but  it  seems  unnecessary  to 
attempt  to  make  a  comparison,  which  can  only  be  appre- 
ciated by  one  who  is  practically  acquainted  with  the  heart- 
sounds,  when  the  sounds  themselves  can  be  so  easily  studied. 

Both  sounds  are  generally  heard  with  distinctness  over 
any  part  of  the  prsecordia.  The  first  sound  is  heard  with  its 
maximum  of  intensity  over  the  body  of  the  heart,  a  little 
below  and  within  the  nipple,  between  the  fourth  and  fifth 
ribs,  and  is  propagated  with  greatest  facility  downwards, 
towards  the  apex.  The  second  sound  is  heard  with  its  max- 
imum of  intensity  at  the  base  of  the  heart,  between  the  nipple 
and  the  sternum,  about  the  locality  of  the  third  rib,  and  is 
propagated  upwards,  along  the  course  of  the  great  vessels. 

The  rhythm  of  the  sounds  bears  a  certain  relation  to  the 
rhythm  of  the  heart's  action,  which  we  have  already  dis- 
cussed ;  the  difference  being,  that  we  here  regard  the  heart's 
action  as  commencing  with  the  systole  of  the  ventricles,  while 
in  following  the  action  of  different  parts  of  the  organ,  we 
followed  the  course  of  the  blood,  and  commenced  with  the 
systole  of  the  auricles.  Laennec,  the  father  of  auscultation, 
was  the  first  to  direct  special  attention  to  the  rhythm  of  these 
sounds,  though  they  had  been  recognized  by  Harvey,  who 
compared  them  to  the  sounds  made  by  the  passage  of  fluids 

1  C.  J.  B.  WILLIAMS,  in  Dunglison's  Human  Physiology.     Philadelphia,  1856, 
voL  L,  p.  393. 


SOUNDS    OF   THE   HEART.  205 

along  the  oesophagus  of  a  horse  when  drinking.1  He  divides 
a  single  revolution  of  the  heart  into  four  parts :  the  first  two 
parts  are  occupied  by  the  first  sound ;  the  third  part  by  the 
second  sound ;  and  in  the  fourth  part  there  is  no  sound.2 
He  regards  the  second  sound  as  following  immediately  after 
the  first.  Some  authors  have  described  a  "  short  silence  "  as 
occurring  after  the  first  sound,  and  a  "  long  silence "  after 
the  second.  The  short  silence,  if  appreciable  at  all,  is  so 
indistinct  that  it  may  practically  be  disregarded. 

Attempts  have  been  made  to  improve  upon  this  division 
of  Laennec,  by  dividing  the  heart's  action  into  three  equal 
parts,  as  is  done  by  M.  Beau ; 3  the  first  being  occupied  by 
the  first  sound,  the  second  by  the  second  sound,  and  the  third, 
silence.  This  hardly  needs  discussion.  M.  Beau  bases  this 
division  upon  a  theory  of  the  production  of  the  sounds  which, 
though  pretty  generally  discussed  by  physiologists,  is,  as  far 
as  we  have  seen,  adopted  by  none,  and  is  so  entirely  opposed 
to  facts  that  it  hardly  demands  comment.  It  is  evident  to 
any  one  who  has  heard  the  sounds  of  the  heart,  that  the  first 
is  longer  than  the  second. 

Most  physiologists  regard  the  duration  of  the  first  sound 
as  a  little  less  than  two-fourths  of  the  heart's  action,  and  the 
second  sound  as  a  little  more  than  one-fourth.  When  we 
come  to  consider  the  mechanism  of  the  production  of  the  two 
sounds,  we  shall  see  that  if  our  views  on  that  point  be  correct, 
the  first  sound  should  occupy  the  period  of  the  ventricular 
systole,  or  four-tenths  of  the  heart's  action,  the  second  sound 
about  three-tenths,  and  the  repose  three-tenths. 
*  The  first  sound  is  relatively  dull,  low  in  pitch,  and  made 
up  of  two  elements :  one,  a  valvular  element,  in  which  it 
resembles  in  character  the  second  sound;  the  other,  an  ele- 
ment which  is  due  to  the  action  of  the  heart  as  a  muscle. 
It  has  been  ascertained  that  all  muscular  contraction  is  at- 

1  Op.  dt,  p.  32. 

9  LAENNEC,  Traite  de  V Auxcuttatian,  Mediate,  Paris,  1837,  tome  in.,  p.  48. 
3  BEAU,   Traite  expcrimentale  et  clinique  d1  Auscultation,  Paris.  1856,  p.  228. 


206  CIKCULATIOK". 

tended  with  a  certain  sound.  To  this  is  added  an  impulsion 
element,  which  is  produced  by  the  striking  of  the  heart  against 
the  walls  of  the  thorax. 

The  second  sound  is  relatively  sharp,  high  in  pitch,  and 
has  but  one  clear,  element,  which  we  have  already  alluded  to 
as  valvular. 

Cause  of  the  Sounds  of  the  Heart. — There  is  now 
scarcely  any  difference  of  opinion  respecting  the  cause  of  the 
second  sound  of  the  heart.  The  experiments  of  Rouanet, 
published  in  1832,  settled  beyond  a  doubt  that  it  was  due  to 
a  closure  of  the  aortic  and  pulmonary  semilunar  valves.  In 
his  essay  upon  this  subject,  Bouanet  acknowledges  his  indebt- 
edness, for  the  first  suggestion  of  this  explanation,  to  Mr 
Carswell,  who  was  at  that  time  prosecuting  his  studies  in 
Paris.1 

The  experiments  by  which  this  is  demonstrated  are  as 
simple  as  they  are  conclusive.  First  we  have  the  experi- 
ments of  Rouanet,  who  imitated  the  second  sound  by  produ- 
cing sudden  closure  of  the  aortic  valves  by  a  column  of  water. 
We  then  have  the  experiments,  even  more  conclusive,  of  the 
British  Commission,  in  which  the  semilunar  valves  were 
caught  up  by  curved  hooks  introduced  through  the  vessels 
of  a  living  animal,  the  ass,  with  the  result  of  abolishing  the 
second  sound,  and  substituting  for  it  a  hissing  murmur. 
When  the  instruments  were  withdrawn,  and  the  valves  per- 
mitted to  resume  their  action,  the  normal  sound  returned.3 

It  is  unnecessary  to  discuss  the  various  theories  which 
have  been  advanced  to  explain  the  second  sound,  as  it  is  now, 
generally  acknowledged  to  he  due  to  the  sudden  closure  of  the 

1  Cydop&dia  of  Anatomy  and  Physiology,  vol.  ii.,  p.  617.  In  this  article,  we 
find  Dr.  Elliott,  of  Carlisle,  alluded  to  as  having  stated  in  his  thesis,  published  in 
1831,  "  that  the  second  sound  of  the  heart  is  dependent  upon  the  rush  of  blood 
from  the  auricles  into  the  ventricles  during  their  diastole,  and  also  upon  the  sud- 
den flapping  inward  of  the  sigmoid  valves  at  the  origin  of  the  large  arteries  by  the 
refluent  blood." 
8  Ibid.,  p.  618. 


CAUSE  OF  THE  SOUNDS  OF  THE  HEART.         207 

semilunar  valves  at  the  orifices  of  the  aorta  and  pulmonary 
artery.  We  remark,  however,  that  the  sound  is  heard  with 
its  maximum  of  intensity  over  the  site  of  these  valves,  and  is 
propagated  along  the  great  vessels,  to  which  they  are  attach- 
ed. It  also  occurs  precisely  at  the  time  of  their  closure ;  i.  e., 
immediately  following  the  ventricular  systole. 

The  cause  of  the  first  sound  of  the  heart  has  not,  until 
within  a  few  years,  been  as  well  understood.  It  was  maintain- 
ed by  Rouanet,  that  this  sound  was  produced  by  the  sudden 
closure  of  the  auriculo- ventricular  valves ',  but  the  situation 
of  these  valves  rendered  it  difficult  to  demonstrate  this  by 
actual  experiment.  We  have  already  seen,  that  while  the 
second  sound  is  purely  valvular  in  its  character,  the  first 
sound  is  composed  of  a  certain  number  of  different  elements ; 
but  auscultatory  experiments  have  been  made  by  which  all 
but  the  valvular  element  are  eliminated,  and  the  character 
of  the  first  sound  made  to  resemble  that  of  the  second.  Con- 
clusive observations  on  this  point  were  made  a  few  years  ago 
by  Dr.  Flint,  constituting  part  of  an  essay  which  received 
the  prize  of  the  American  Medical  Association  in  1858.1 

The  following  facts  were  developed  in  this  essay : 

1.  If  a  folded  handkerchief  be  placed  between  the  stetho- 
scope and  integument,  the  first  sound  is  divested  of  some  of 
its  most  distinctive  features.     It  loses  the  quality  of  impul- 
sion, and  presents  a  well-marked  valvular  quality. 

2.  In  many  instances,  when  the  stethoscope  is  applied  to 
the  praecordia,  while  the  subject  is  in  a  recumbent  posture,  and 
the  heart  by  force  of  gravity  is  removed  from  the  anterior 
wall  of  the  thorax,  the  first  sound  becomes  purely  valvular 
in  character,  and  as  short  as  the  second. 

3.  When  the  stethoscope  is  applied  to  the  chest  a  little 
distance  from  the  point  where  the  first  sound  is  heard  with 
its  maximum  of  intensity,  it  will  present  only  its  valvular 
element. 

1  AUSTIN  FLINT,  Prize  Essay  on  the  Heart-Sounds  in  Health  and  Disease. 
—  Transactions  of  the  American  Medical  Association,  1858. 


208  CIRCULATION. 

These  facts,  to  which  we  may  add  the  modifications  of 
the  first  sound  in  disease,  so  as  to  leave  only  the  valvular  ele- 
ment, taken  in  connection  with  the  fact  that  the  first  sound 
occurs  when  the  ventricles  contract,  and  necessarily  accom- 
panies the  closure  of  the  auriculo-ventricular  valves,  show 
pretty  conclusively  that  these  valves  produce  at  least  a  cer- 
tain element  of  the  sound.  In  further  support  of  this  opinion, 
we  have  the  fact  that  the  first  sound  is  heard  with  its  maxi- 
mum of  intensity  over  the  site  of  the  valves,  and  is  propa- 
gated downwards  along  the  ventricles,  to  which  the  valves 
are  attached. 

Actual  experiments  are  not  wanting  to  confirm  the  above 
view.  Chauveau  andFaivre1  have  succeeded  in  abolishing 
the  first  sound  by  the  introduction  of  a  wire  ring  through  a 
little  opening  in  the  auricle  into  the  auriculo-ventricular  ori- 
fice, so  arranged  as  to  prevent  the  closure  of  the  valves. 
When  this  is  done,  the  first  sound  is  lost ;  but  on  taking  it  out 
of  the  opening,  the  sound  returns.  These  observers  also 
abolished  the  first  sound  by  introducing  a  small  curved 
tenotomy-knife  through  the  auriculo-ventricular  orifice,  and 
dividing  the  chordae  tendinese.  In  this  experiment  a  loud  rush- 
ing murmur  took  the  place  of  the  sound.  We  have  already 
alluded  to  the  experiment  of  introducing  the  finger  through 
an  opening  in  the  auricle ;  if  this  be  done,  and  the  heart  be 
auscultated  at  the  same  time,  the  valves  will  be  felt  striking 
against  the  finger  in  unison  with  the  first  sound. 

The  above  observations  and  experiments  settle  beyond 
question  the  fact  that  the  closure  of  the  auriculo-ventricular 
valves  produces  one  element  of  the  first  sound. 

The  other  elements  which  enter  into  the  composition  of 
the  first  sound  are  not  as  prominent  as  the  one  we  have  just 
considered,  though  they  serve  to  give  it  its  prolonged  and 
"  booming  "  character.  These  elements  are,  a  sound  like  that 
produced  by  any  large  muscle  during  its  contraction,  called 

1  Op.  cit.,  pp.  30  and  81. 


CAUSE   OF   THE   SOUNDS   OF  THE   HEART.  209 

by  some  the  muscular  murmur,  and  the  sound  produced  by 
the  impulse  of  the  heart  against  the  walls  of  the  chest. 

The  muscular  sound  has  been  recognized  by  Wollaston, 
Laennec,  and  others,  and  by  Laennec  was  supposed  to  be 
the  sole  cause  of  the  first  sound  of  the  heart.  This  observer 
attributed  the  first  sound  to  the  muscular  action  of  the  ven- 
tricles, and  the  second  to  the  action  of  the  auricles.  There 
can  be  no  doubt  but  that  this  is  one  of  the  elements  of  the  first 
sound ;  and  it  is  this  which  gives  it  its  prolonged  character, 
when  the  stethoscope  is  applied  over  the  body  of  the  organ, 
as  the  sound  produced  in  muscles  continues  during  the  whole 
period  of  their  contraction.  Admitting  this  to  be  an  element 
of  the  first  sound,  we  can  understand  how  its  duration  must 
necessarily  coincide  with  the  ventricular  systole.  We  can 
appreciate,  also,  how  all  but  the  valvular  element  is  eliminated 
when  the  stethoscope  is  moved  from  the  body  of  the  heart, 
the  muscular  sound  not  being  propagated  as  completely  as 
the  sound  made  by  the  closure  of  the  valves. 

The  impulse  of  the  heart  against  the  walls  of  the  thorax 
also  contributes  to  produce  the  first  sound.  This  is  demon- 
strated by  noting  the  difference  in  the  sound  when  the  sub- 
ject is  lying  upon  the  back,  and  when  he  is  upright ;  or  by 
interposing  any  soft  substance  between  the  stethoscope  and 
the  chest,  or  by  auscultating  the  heart  after  the  sternum  has  been 
removed.  Under  these  circumstances  the  first  sound  loses  its 
booming  character,  retaining,  however,  the  muscular  element, 
when  the  instrument  is  applied  to  the  exposed  organ.  It  was 
thought  by  Magendie  that  the  shock  of  the  heart  against  the 
chest  was  the  sole  cause  of  the  first  sound.1  This  observer 
maintained  that  when  the  sternum  is  removed  in  a  living  ani- 
mal, the  first  sound  cannot  be  heard  over  the  heart.  This, 
however,  is  not  the  fact ;  and  though  the  element  of  impul- 
sion enters  into  the  composition  of  the  first  sound,  the  view 
that  it  is  the  sole  cause  of  this  sound  is  not  tenable. 

The  first  sound  of  the  heart  is   complex.      It  is  pro 

1  MILNE-EDWARDS,  Lemons  sur  la  Physiologic,  etc.,  tome  iv.,  p.  3S. 
14 


210  CIRCULATION. 

duced  by  the  sudden  closure  of  the  auriculo-ventricular 
valves  at  the  beginning  of  the  ventricular  systole ;  to  which 
are  superadded  the  muscular  sound,  due  to  the  contraction 
of  the  muscular  fibres  of  the  heart,  and  the  impulsion  sound 
due  to  the  shock  of  the  organ  against  the  walls  of  the  thorax. 

The  second  sound  is  simple.  It  is  produced  by  the  sud- 
den closure  of  the  aortic  and  pulmonary  semilunar  valves, 
immediately  following  the  ventricular  systole. 

It  is  of  the  greatest  importance,  with  reference  to  pathol- 
ogy, to  have  a  clear  idea  of  the  currents  of  blood  through  the 
heart,  with  their  exact  relation  to  the  sounds  and  intervals. 

At  the  commencement  of  the  first  sound,  the  blood  is 
forcibly  thrown  from,  the  ventricles  into  the  pulmonary 
artery  on  the  right  side  and  the  aorta  on  the  left,  and  the 
auriculo-ventricular  valves  are  suddenly  closed.  During  the 
entire  period  occupied  by  this  sound,  the  blood  is  flowing 
rapidly  through  the  arterial  orifices,  and  the  auricles  are  re- 
ceiving blood  slowly  from  the  vense  cavse  and  the  pulmonary 
veins. 

"While  the  second  sound  is  produced,  the  ventricles  hav- 
ing become  suddenly  relaxed,  the  recoil  of  the  arterial  walls, 
acting  upon  the  column  of  blood,  immediately  closes  the 
semilunar  valves  upon  the  two  sides.  The  auricles  continue 
to  dilate,  and  the  ventricles  are  slowly  receiving  blood. 

Immediately  following  the  second  sound,  during  the  first 
part  of  the  interval  the  auricles  become  fully  dilated ;  and 
in  the  last  part  of  the  interval  immediately  preceding  the 
first  sound,  the  auricles  contract,  and  the  ventricles  are  fully 
dilated.  This  completes  a  single  revolution  of  the  heart. 


CHAPTER  Y. 

FREQUENCY   OF   THE   HEARTS    ACTION. 

Frequency  of  the  heart's  action — Influence  of  age — Influence  of  digestion — Influ- 
ence of  posture  and  muscular  exertion — Influence  of  exercise — Influence  of 
temperature — Influence  of  respiration  on  the  action  of  the  heart — Cause  of 
the  rhythmical  contractions  of  the  heart — Influence  of  the  nervous  system  on 
the  heart — Division  of  the  pneumogastrics — Galvanization  of  the  pneumogas- 
trics — Causes  of  the  arrest  of  action  of  the  heart — Blows  upon  the  epigas- 
trium. 

Frequency  of  the  Heart's  Action. — Physicians  have  al- 
ways attached  the  greatest  importance  to  the  frequency  of 
the  action  of  the  heart,  as  one  of  the  great  indications  of  the 
general  condition  of  the  system.  The  variations  which  are 
met  with  in  health,  dependent  upon  age,  sex,  muscular  activ- 
ity, the  condition  of  the  digestive  system,  etc.,  point  to  the 
fact  that  the  action  of  the  heart  is  closely  allied  to  the  various 
functions  of  the  economy,  and  readily  sympathizes  with  their 
derangements.  As  each  ventricular  systole  is  followed  by 
an  expansion  of  the  arteries  which  is  readily  appreciated  by 
the  touch,  it  is  more  convenient  to  study  the  succession  of 
these  movements  by  exploring  the  vessels,  than  by  examina- 
tion of  the  heart  itself.  Leaving  out  certain  of  the  qualities 
of  the  pulse,  this  becomes  an  exact  criterion  of  the  acts  of  the 
heart. 

The  number  of  pulsations  of  the  heart  is  not  far  from 
seventy  per  minute  in  an  adult  male,  and  from  six  to  ten 


212  CIRCULATION. 

more  in  the  female.1  There  are  individual  cases  where  the 
pulse  is  normally  much  slower  or  more  frequent  than  this,  a 
fact  which  must  be  remembered  when  examining  the  pulse 
in  disease.  It  is  said  that  the  pulse  of  Napoleon  I.  was  only 
forty  per  minute.  Dr.  Dun^lison  mentions  a  case  which 
came  under  his  own  observation,  in  which  the  pulse  was  on 
an  average  thirty-six  per  minute.  The  same  author  states 
that  the  pulse  of  Sir  William  Congreve  wTas  never  below  one 
hundred  and  twenty-eight  per  minute,  in  health.2  It  is  by 
no  means  unfrequent  to  find  a  healthy  pulse  of  a  hundred  or 
more  per  minute. 

Influence  of  Age  and  Sex. — In  both  the  male  and  female, 
observers  have  constantly  found  a  great  difference  in  the  rapidi- 
ty of  the  heart's  action  at  different  periods  of  life.  The  observa- 
tions of  Dr.  Guy  on  this  point  are  very  numerous,  and  were 
made  with  the  utmost  care  with  regard  to  the  conditions  of  the 
system,  at  the  time  the  pulse  was  taken,  in  each  case.  All  were 
taken  at  the  same  hour,  and  with  the  subject  in  a  sitting  posture. 

Dr.  Guy  found  the  pulsations  of  the  heart  in  the  foetus 
to  be  pretty  uniformly  140  per  minute.  At  birth  the  pulse 
is  136.  It  gradually  diminishes  during  the  first  year  to  about 
128.  The  second  year  the  diminution  is  quite  rapid,  the 
tables  of  Dr.  Guy  giving  107  as  the  mean  frequency  at  two 
years  of  age.  After  the  second  year,  the  frequency  progres- 
sively diminishes  until  adult  life,  when  it  is  at  its  minimum, 
which  is  about  70  per  minute.  It  is  a  common,  but  erro- 
neous, impression  that  the  pulse  diminishes  in  frequency  in 
old  age.  On  the  contrary,  numerous  observations  show  that 
at  the  latter  periods  of  life  the  movements  of  the  heart  be- 
come slightly  accelerated,  ranging  from  75  to  80. 

During  early  life  there  is  no  marked  and  constant  differ- 

1  Most  of  the  facts  which  will  be  referred  to  with  regard  to  the  frequency  of 
the  pulse  are  taken  from  the  article  of  Dr.  Guy  (Pulse)  in  Todd's  Cyclopaedia  of 
Anatomy  and  Physiology. 

a  Human  Physiology.    Philadelphia,  1856,  vol.  i.,  p.  445. 


FREQUENCY   OF   THE    HEART?8   ACTION.  213 

ence  in  the  rapidity  of  the  pulse  in  the  sexes ;  but  towards 
the  age  of  puberty,  the  development  of  the  sexual  peculiarities 
is  accompanied  with  an  acceleration  of  the  heart's  action  in 
the  female,  which  continues  even  into  old  age.  The  differ- 
ence at  different  ages  is  shown  in  the  following  table,  com- 
piled by  Milne-Edwards  from  the  observations  of  Dr.  Guy : ; 

AGES.  MALES.  FEMALES. 

Average  Pulsations.  Average  Pulsations. 

From  2  to  7  years        .        .        97       ....        98 


8 

14 
21 
28 
35 
42 


14  "   •    •    .84 94 

21  "  ..    76   ....    82 

28  "  .    .    .  73  .    .    .    .    .80 

35  "  .    .    70   .  '  .    .    .    78 

42  "  .  68  .              .  78 


49  "  ..   70   ....  77 

"  49  "  56  "  .  .67 76 

"  56  "  63  "  .    .    68      .    .    .  77 

"  63  "  70  "  .  .70 78 

"  70  "  77  u  .   .    67   .    .   .    .  81 

"  77  "  84  "  .  .71 82 

Influence  of  Digestion. — The  condition  of  the  digestive 
system  has  a  marked  influence  on  the  rapidity  of  the  pulse. 
According  to  observations  cited  by  Milne-Edwards,2  there  is 
an  increase  in  the  pulse  of  from  five  to  ten  beats  per  minute 
after  each  meal.  Prolonged  fasting  diminishes  its  frequency 
from  twelve  to  fourteen  beats.  Alcohol  first  diminishes,  and 
afterwards  accelerates,  the  pulse.  Coffee  is  said  by  the  same 
author  to  accelerate  the  pulse  in  a  marked  degree.  It  has 
been  ascertained  that  the  pulse  is  accelerated  to  a  greater 
degree  by  animal  than  by  vegetable  food.  These  variations 
have  long  been  recognized  by  physiologists. 

Influence  of  Posture  and  Muscular  Exertion. — It  has 
been  observed  that  attitude  has  a  very  marked  influence  upon, 
the  rapidity  of  the  action  of  the  heart.  Experiments  of  a 

1  Le$ons  sur  la  Pkysiologie,  tome  iv.,  p.  62. 

2  Loc.  cit. 


214:  CIRCULATION. 

very  interesting  character  have  been  made  by  Dr.  Guy  and 
others,  with  a  view  to  determine  the  difference  in  the  pulse 
in  different  postures.  In  the  male,  there  is  a  difference  of 
about  ten  beats  between  standing  and  sitting,  and  fifteen 
beats  between  standing  and  the  recumbent  posture.  In  the . 
female,  the  variations  with  p^ition  are  not  so  great.  The 
average  given  by  Dr.  Guy  is,  for  the  male :  .  standing,  81 ; 
sitting,  71 ;  lying,  66 ; — for  the  female :  standing,  91 ;  sitting, 
84 ;  lying,  80.  This  is  given  as  the  average  of  a  large  num- 
ber of  observations.  There  were  a  few  instances,  however, 
in  which  there  was  scarcely  any  variation  with  posture,  and 
some  in  which  the  variation  was  much  greater  than  the 
average.  In  the  inverted  posture,  the  pulse  was  found  to  be 
reduced  about  fifteen  beats. 

The  question  at  once  suggests  itself  whether  the  accelera- 
tion of  the  pulse  in  sitting  and  standing  may  not  be  due,  in 
some  measure,  to  the  muscular  effort  required  in  making  the 
change  of  posture.  This  is  answered  by  the  further  experi- 
ments of  Dr.  Guy,  in  which  the  subjects  were  placed  on  a 
revolving  board,  and  the  posture  changed  without  any  mus- 
cular effort.  The  same  results  as  those  cited  above  were 
obtained  in  these  experiments ;  showing  that  the  difference 
is  due  to  the  position  of  the  body  alone.  In  a  single  obser- 
vation, Dr.  Guy  found  the  pulse,  standing,  to  be  89 ;  lying, 
77;  difference,  12.  With  the  posture  changed  without  any 
muscular  effort,  the  results  were :  standing,  87 ;  lying,  74 ; 
difference,  13. 

Various  theoretical  explanations  of  these  variations  have 
been  offered  by  physiologists;  but  Dr.  Guy  seems  to  have 
settled  experimentally  that  the  acceleration  is  due  to,  the  mus- 
cular effort  required  to  maintain  the  body  in  the  sitting  and 
standing  positions.  The  following  are  the  results  of  experi- 
ments which  bear  conclusively  on  this  point,  in  which  it  is 
shown  that  when  the  body  is  carefully  supported  in  the  erect 
or  sitting  posture,  so  as  to  be  maintained  without  muscular 
effort,  the  pulse  is  less  frequent  than  when  the  subject  is 


FBEQUENCY    OF   THE    HEAET's   ACTION.  215 

standing;  and  furthermore  that  the  pulse  is  accelerated,  in 
the  recumbent  posture,  when  the  body  is  only  partially  sup- 
ported : 

"1.  Difference  between  the  pulse  in  the  erect  posture, 
without  support,  and  leaning  in  the  same  posture,  in  an 
average  of  twelve  experiments  on  the  writer,  12  beats;  and 
on  an  average  of  eight  experiments  on  other  healthy  males, 
8  beats. 

"  2.  Difference  in  the  frequency  of  the  pulse  in  the  recum- 
bent posture,  the  body  fully  supported,  and  partially  sup- 
ported, 14  beats,  on  an  average  of  five  experiments. 

"  3.  Sitting  posture  (mean  often  experiments  on  the  writer), 
back  supported,  80 ;  unsupported,  87 ;  difference,  7  beats. 

"  4.  Sitting  posture  with  the  legs  raised  at  right  angles  with 
the  body  (average  of  twenty  experiments  on  the  wrriter),  back 
unsupported,  86;  supported,  68;  difference,  18  beats.  An 
average  of  fifteen  experiments  of  the  same  kind  on  other 
healthy  males  gave  the  following  numbers  :  "back  unsupport- 
ed, 80 ;  supported,  68 ;  a  difference  of  12  beats." 1 

Influence  of  Exercise. — It  is  a  fact  generally  appreciated 
that  muscular  exertion  increases  the  frequency  of  the  pul- 
sations of  the  heart ;  and  the  experiments  just  cited  show 
that  the  difference  in  rapidity,  which  is  by  some  attributed 
to  change  in  posture  (some  positions,  it  is  fancied,  offering 
fewer  obstacles  to  the  current  of  blood  than  others),  is  in 
reality  due  to  muscular  exertion.  Every  one  knows  that  the 
action  of  the  heart  is  much  more  rapid  after  violent  exertion, 
such  as  running,  lifting,  etc.  Experiments  on  this  point 
date  from  quite  a  remote  period.  Bryan  Robinson,  who 
published  a  treatise  on  the  "Animal  Economy"  in  1734, 

1  TODD'S  Cyclopedia  of  Anatomy  and  Physiology,  vol.  iv.,  p.  188.  There  is 
an  apparent  contradiction  between  these  results,  and  results  of  the  experiments 
with  the  "  revolving  board."  It  is  probable,  however,  that  the  subjects  experi- 
mented upon  with  the  board  were  simply  placed  in  the  erect  posture  without 
muscular  effort,  but  maintained  themselves  in  position  without  any  aid. 


CIRCULATION. 

states,  as  the  result  of  observation,  that  a  man  in  the  recum 
bent  position  has  64  pulsations  per  minute ;  after  a  slow  walk, 
78 ;  after  walking  a  league  and  a  half  in  an  hour,  100 ;  and 
140  to  150  after  running  with  all  his  might.1  This  general 
statement,  which  has  been  repeatedly  verified,  shows  the 
powerful  influence  of  the  muscuiar  system  on  the  heart.  The 
fact  is  so  familiar  that  it  need  not  be  further  dwelt  upon. 

The  influence  of  sleep  upon  the  action  of  the  heart  reduces 
itself  almost  entirely  to  the  proposition,  that  during  this  con- 
dition, we  have  an  entire  absence  of  muscular  effort,  and 
consequently  the  number  of  beats  is  less  than  when  the  in- 
dividual is  aroused.  It  has  been  found  that  there  is  no  differ- 
ence in  the  pulse  between  sleep  and  perfect  quiet  in  the 
recumbent  posture.  This  fact  obtains  in  the  adult  male ;  but 
it  is  said  by  Quetelet  that  there  is  a  marked  difference  in 
females  and  young  children,  the  pulse  being  always  slower 
during  sleep.2 

Influence  of  Temperature. — The  influence  of  extremes  of 
temperature  upon  the  heart  is  very  decided.  The  pulse  may 
be  doubled  by  remaining  a  very  few  minutes  exposed  to  ex- 
treme heat.  Bence  Jones  and  Dickinson  have  ascertained 
that  the  pulse  may  be  very  much  reduced  in  frequency,  for 
a  short  time,  by  the  cold  douche.3  It  has  also  been  remarked 
that  the  pulse  is  habitually  more  rapid  in  warm  than  in  cold 
climates. 

Though  many  circumstances  materially  affect  the  rapidi- 
ty of  the  heart's  action,  they  do  not  complicate,  to  any  great 
extent,  our  examinations  of  the  pulse  in  disease.  In  cases 
which  present  considerable  febrile  movement,  the  patient  is 
generally  in  the  recumbent  posture.  The  variations  induced 
by  violent  exercise  are  easily  recognized,  while  those  depend- 
ent upon  temperature,  the  condition  of  the  digestive  system, 
etc.,  are  so  slight  that  they  may  practically  be  disregarded. 

1  MILNE-EDWARDS,  Lemons  sur  la  Physiologic,  tome  iv.,  p.  68. 

2  Ibid. 

3  Journal  de  la  Physiologic,  1858,  tome  i.,  p.  72. 


INFLUENCE   OF  RESPIRATION  ON   THE   HEART.  217 

It  is  necessary  to  bear  in  mma,  however,  the  variations  which 
exist  in  the  sexes,  and  at  different  periods  of  life,  as  well  as 
the  possibility  of  individual  peculiarities,  when  the  action  of 
the  heart  may  be  extraordinarily  rapid  or  slow. 

Influence  of  Respiration  upon  the  Action  of  the  Hea/rt. — 
The  relations  between  the  functions  of  circulation  and  respi- 
ration are  very  intimate.  One  function  cannot  go  on  without 
the  other.  If  circulation  be  arrested,  the  muscles,  being  no 
longer  supplied  with  fresh  blood,  soon  lose  their  contractile 
power,  and  respiration  ceases.  We  shall  also  find  that  circu- 
lation is  impossible  if  respiration  be  permanently  arrested. 
When  respiration  is  imperfectly  performed,  the  action  of  the 
heart  is  slow  and  labored.  All  physicians  are  familiar  with 
the  slow,  full  pulse,  indicating  labored  action  of  the  heart, 
which  occurs  in  profound  coma.  The  effects  of  arrest  of 
respiration  are  marked  in  all  parts  of  the  circulatory  system, 
arteries,  capillaries,  and  veins  ;  but  the  disturbances  thus  pro- 
duced all  react  upon  the  heart,  and  the  modifications  which 
take  place  in  the  action  of  this  organ  are  of  the  greatest  in- 
terest and  importance. 

If  the  heart  be  exposed  in  a  living  animal,  and  artificial 
respiration  be  kept  up,  though  the  pulsations  are  increased  in 
frequency  and  diminished  in  force,  after  a  time  they  become 
perfectly  regular,  and  continue  thus  as  long  as  air  is  ade- 
quately supplied  to  the  lungs.  Under  these  circumstances 
we  have  the  respiration  entirely  at  our  command,  and  can 
study  the  effects  of  its  arrest  upon  the  heart  with  the  greatest 
facility.  If  we  arrest  respiration,  we  observe  the  following 
changes  in  the  action  of  the  heart : 

For  a  few  seconds  pulsations  go  on  as  usual ;  but  in  about 
a  minute  they  begin  to  diminish  in  frequency.  At  the  same 
time  the  heart  becomes  engorged  with  blood,  a  condition 
which  rapidly  increases.  For  a  time  its  contractions  are 
competent  to  discharge  the  entire  contents  of  the  left  ventri- 
cle into  the  arterial  system,  and  a  cardiometer  applied  to  an 


218  CIRCULATION. 

artery  will  indicate  a  great  increase  in  the  pressure  of  blood, 
and  a  corresponding  increase  in  the  movements  of  the  mer- 
cury will  be  noted  at  each  action  of  the  heart ;  indicating 
that  the  organ  is  acting  with  an  abnormal  vigor.  If  respira- 
tion be  still  discontinued,  the  engorgement  becomes  intense, 
the  heart  at  each  diastole  being  distended  to  its  utmost  capa- 
city. It  now  becomes  incapable  of  emptying  itself;  the  con- 
tractions become  very  unfrequent,  perhaps  three  or  four  in  a 
minute,  and  are  progressively  enfeebled.  The  organ  is  dark, 
almost  black,  owing  to  the  circulation  of  venous  blood  in  its 
substance.  If  respiration  be  not  resumed,  this  distention 
continues,  the  contractions  become  less  frequent  and  more 
feeble,  and  in  a  few  minutes  entirely  cease. 

The  arrest  of.  the  action  of  the  heart,  under  these  circum- 
stances, is  chiefly  mechanical.  The  UD aerated  blood  passes 
with  difficulty  through  the  capillaries  of  the  system,  and  as 
the  heart  is  constantly  at  work,  the  arteries  become  immensely 
distended.  This  is  proven  by  the  great  increase  in  the  arte- 
rial pressure,  while  these  vessels  are  full  of  black  blood.  If 
we  now  closely  examine  the  heart  and  great  vessels,  we  are 
able  to  note  distinctly  the  order  in  which  they  become  dis- 
tended. These  phenomena  were  particularly  noticed  and  de- 
scribed by  Prof.  Dalton,  and  they  demonstrate  conclusively 
that  in  asphyxia  the  obstruction  to  the  circulation  commences, 
not  in  the  lungs,  as  is  commonly  supposed,  but  in  the  capil- 
laries of  the  system,  and  is  propagated  backwards  to  the  heart 
through  the  arteries. 

"  The  obstacle  to  the  passage  of  venous  blood  through  the 
capillaries,  therefore,  is  partial,  not  complete.  But  it  is  still 
sufficient  to  produce  an  immediate  backward  engorgement  of 
the  arterial  system.  Then  the  aorta  becomes  distended  at  its 
origin,  and  the  left  ventricle  and  left  auricle  in  succession, 
being  unable  to  relieve  themselves  of  blood  through  the  arte- 
rial system,  become  distended  in1  a  similar  manner.  During 
this  time  the  same  kijid  of  engorgement  takes  place  in  the  pul- 
monary artery  and  the  right  cavities  of  the  heart ;  though 


INFLUENCE   OF   RESPIRATION  ON   THE   HEAKT.  219 

the  distention  of  the  pulmonary  artery  is  never  so  excessive 
as  that  of  the  aorta,  either  because  there  is  less  obstacle  to 
the  passage  of  venous  blood  through  the  lungs  than  through 
the  general  capillaries,  or  because  the  injecting  force  of  the 
riffht  ventricle  is  less  than  that  of  the  left,  or  because  less 

O  •  ' 

blood  is  supplied  by  the  capillaries  to  the  veins,  and  by  the 
veins  to  the  right  side  of  the  heart.  In  either  case  the  prin- 
cipal accumulation  is  certainly  in  the  arterial  system." 1 

The  distention  of  the  heart  in  asphyxia  is  therefore  due  to 
the  fact  that  uhaerated  blood  cannot  circulate  in  the  systemic 
capillaries.  "When  thus  distended,  its  muscular  fibres  become 
paralyzed,  like  any  muscle  after  a  severe  strain. 

If  respiration  be  resumed  at  any  time  before  the  heart's 
action  has  entirely  ceased,  the  organ  in  a  few  moments  re- 
sumes its  normal  function.  "We  first  notice  a  change  from 
the  dusky  hue  it  has  assumed  to  a  vivid  red,  which  is  owing 
to  the  circulation  of  arterial  blood  in  its  capillaries.  The 
distention  then  becomes  gradually  relieved,  and  for  a  few 
moments  the  pulsations  are  abnormally  frequent.  If  we  now 
open  an  artery,  it  will  be  found  to  contain  red  blood.  An  in- 
strument applied  to  an  artery  will  show  a  diminution  of 
arterial  pressure  and  force  of  the  heart's  action,  if  the  arrest 
of  respiration  has  been  carried  only  far  enough  to  moderately 
distend  the  heart ;  or  an  increase  in  the  pressure  and  force  of 
the  heart,  if  its  action  has  been  nearly  arrested.  A  few  mo- 
ments of  regular  insufflation  will  cause  the  pulsations  to  re- 
sume their  normal  character  and  frequency. 

In  the  human  subject,  the  effects  of  temporary  or  perma- 
nent arrest  of  respiration  on  the  heart,  are  undoubtedly  the 
same  as  those  observed  in  experiments  upon  the  warm-blood- 
ed animals.  In  the  same  way,  also,  it  is  possible  to  restore 
the  normal  action  of  the  organ,  if  respiration  be  not  too  long 
suspended,  by  the  regular  introduction  of  fresh  air  into  the 
lungs.  The  numerous  examples  of  animation  restored  by 

1  D  ALTON,  Lectures  on  the  Physiology  of  the  Circulation,  published  in  the 
Buffalo  Medical  Journal  and  New  York  Review,  Lecture  III.,  April,  1860. 


220  CIRCULATION. 

artificial  respiration,  in  drowning,  etc.,  particularly  by  what 
is  known  as  the  Marshall  Hall  method,  are  evidence  of  this 
fact.  In  cases  of  asphyxia,  those  measures  by  which  artificial 
respiration  is  most  effectually  maintained  have  been  found 
most  efficient. 

Certain  individuals  have  the  power  of  temporarily  arrest- 
ing the  action  of  the  heart  by  a  voluntary  suspension  of  res- 
piration. The  most  remarkable  case  of  this  kind  on  record 
is  that  of  Colonel  Townshend,  which  is  quoted  in  many 
works  on  physiology.1  Col.  T.  was  said  to  be  able  to  arrest 
respiration  and  the  action  of  the  heart  so  completely  as  to 
simulate  death.  "When  in  this  condition,  the  pulse  was  not 
perceptible  at  the  wrist  nor  over  the  prsecordia,  a  mirror  held 
before  the  mouth  was  not  tarnished,  and  he  was  to  all  ap- 
pearances dead.  On  one  occasion,  in  the  presence  of  several 
medical  gentlemen,  he  remained  in  this  condition  for  half  an 
hour  ;  afterwards  the  functions  of  respiration  and  circulation 
becoming  gradually  reestablished.  This,  to  say  the  least,  is  a 
very  remarkable  case,  but  is  credited  by  many  physiologists. 

Cause  of  the  Rhythmical  Contractions  of  the  Heart. 

The  phenomena  attending  the  action  of  the  heart  pre- 
sent few  difficulties  in  their  investigation,  compared  with  the 
study  of  the  cause  of  the  regular  contractions  and  relaxations, 
which  commence  early  in  foetal  development,  to  terminate 
only  with  life.  This  interesting  question  has  long  engaged 
the  attention  of  physiologists,  and  has  been  the  subject  of 
numerous  experiments  and  speculations.  It  would  be  idle 
to  follow  the  various  theories  which  have  been  offered  to 
account  for  this  constant  movement,  except  as  a  subject  of 
purely  historical  interest ;  for  many  of  them  are  based  upon 
a  very  imperfect  knowledge  of  the  phenomena  of  the  circu- 

1  DUNGLISON,  Human  Physiology,  Philadelphia,  1856.     Eighth  edition,  vol.  i., 
p.  405. 


CAUSE  OF  THE  RHYTHMICAL  CONTRACTIONS  OF  THE  HEAKT,      221 

lation,  and  have  fallen  to  the  ground,  as  science  has  advanced. 
At  the  present  day,  though  we  are  perhaps  as  far  as  ever 
from  a  knowledge  of  the  actual  cause  of  the  regular  move- 
ments, we  are  pretty'well  acquainted  with  the  various  condi- 
tions which  modify  and  regulate  them,  and  have  arrived  at  a 
limit  of  knowledge  which  there  seems  little  prospect  of  ex- 
ceeding. The  enthusiastic  dreamers  of  past  ages  hoped  to 
discover  the  seat  of  the  soul  and  arrive  at  the  principle  of 
life,  but  we  are  as  much  in  the  dark  as  were  they  with  regard 
to  the  cause  of  the  various  vital  phenomena.  We  know,  for 
example,  how  to  induce  contraction  in  a  living  muscle,  or 
one  which  is  just  separated  from  the  organism  and  has  not 
yet  lost  what  we  call  its  vital  properties  y\)Mi  we  must  confess 
our  utter  ignorance  when  we  ask  ourselves  why  it  acts 
in  response  to  a  stimulus.  The  wonderful  advances  we 
have  made  in  chemistry  and  microscopic  anatomy  do  not 
disclose  the  vital  principle ;  and  when  we  come  to  examine 
the  various  conditions  under  which  the  heart  will  continue 
its  contractions,  we  are  arrested  by  the  impossibility  of  fathom- 
ing the  mystery  of  the  cause  of  contraction.  The  heart  is, 
anatomically,  very  much  like  the  voluntary  muscles ;  but  it 
has  a  constant  function  to  perform,  and  will  act  without  any 
palpable  excitation,  while  the  latter,  which  have  an  occa- 
sional function,  act  only  under  the  influence  of  a  natural 
stimulus  like  the  nervous  force,  or  artificial  irritation. 
The  movements  of  the  heart  are  not  the  only  examples  of, 
what  seems  to  be,  spontaneous  action.  The  ciliated  epithe- 
lium is  in  motion  from  the  beginning  to  the  end  of  life,  and 
will  continue  for  a  certain  time  even  after  the  cells  are  de- 
tached from  the  organism.  This  motion  cannot  be  explained, 
unless  we  call  it  an  explanation  to  say  that  it  is  dependent 
on  vital  properties. 

But  if  we  are  yet  ignorant  of  the  absolute  cause  of  the 
rhythmical  contraction  of  the  heart,  we  are  pretty  well  ac- 
quainted with  the  influences  which  render  its  action  regular, 
powerful,  and  sufficient  for  the  purposes  of  the  economy.  It 


222  CIRCULATION. 

will  facilitate  our  comprehension  of  this,  to  compare  this 
action  with  that  of  the  ordinary  voluntary  muscles. 

In  the  first  place,  every  one  knows  that  the  action  of  the 
heart  is  involuntary.  We  can  neither  arrest,  retard,  nor 
accelerate  its  pulsations  by  a  direct  effort  of  the  will.  In  this 
statement  we  of  course  except  those  examples  of  arrest  by 
the  stoppage  of  respiration,  or  acceleration  by  violent  exer- 
cise, etc.  In  this  respect  the  heart  differs  from  certain  mus- 
cles, like  the  muscles  of  respiration,  which  act  involuntarily, 
it  is  true,  but  whose  action  may  be  temporarily  arrested  or 
accelerated  by  a  direct  voluntary  effort. 

The  last-mentioned  fact  gives  us  the  precise  difference 
between  the  heart  and  all  other  striped  muscles.  All  of 
them,  in  order  to  contract,  must  receive  a  stimulus,  either 
natural  or  artificial.  The  natural  stimulus  comes  from  the 
nervous  centres,  and  is  conducted  by  the  nerves.  If  the  nerves 
going  to  any  of  the  respiratory  muscles,  for  example,  be 
divided,  the  muscle  is  paralyzed,  and  will  not  contract  with- 
out some  kind  of  irritation.  Connection  with  the  nervous 
system  does  not  seem  necessary  to  the  action  of  the  heart,  for 
it  will  contract,  especially  in  the  cold-blooded  animals,  some 
time  after  its  removal  from  the  body. 

When  a  muscle  has  been  removed  from  the  body,  and  is 
subjected  to  a  stimulus,  such  as  galvanism,  mechanical  or 
chemical  irritation,  it  is  thrown  into  contraction ;  but  if  care- 
fully protected  from  irritation,  will  remain  quiescent.  Con- 
traction in  this  instance  is  evidently  produced  by  the  appli- 
cation of  the  stimulus  ;  but  the  question  arises,  Why  does  the 
muscle  thus  respond  to  stimulation  ?  This  is  a  question  which 
it  is  impossible  to  answer  satisfactorily,  but  one  concerning 
which  our  ideas,  since  the  time  of  Haller,  have  assumed  a 
definite  form.  This  great  physiologist  called  the  property 
which  causes  the  muscle  thus  to  contract,  irritability  •  which 
is  nothing  more  nor  less  than  an  unexplained  property  in- 
herent in  the  muscle,  and  continuing  as  long  as  it  retain^  its 
absolute  physical  and  chemical  integrity.  More  than  a  hun- 


CAUSE  OF  THE  RHYTHMICAL  CONTRACTIONS  OF  THE  HEART.    223 

dred  years  ago,  Haller  described  certain  tissues  of  the  body 
which  possessed  this  "irritability,"  such  as  the  muscles, 
stomach,  bladder,  etc.,  and  the  different  degrees  of  irritability 
with  which  each  one  was  endowed.1  He  applied  this  theory 
to  the  action  of  the  heart,  which  he  considered  as  the  part 
endowed  with  irritability  to  the  highest  degree.  His  theory 
of  the  action  of  the  heart  was  that  its  rhythmical  contraction 
depended  upon  the  irritability  inherent  in  its  muscular  fibres. 
He  was  far  from  denying  the  various  influences  which  modi- 
fied this  action,  but  regarded  its  actual  power  of  contraction 
as  independent.  It  will  be  interesting  to  review  some  of  the 
facts  which  were  established  by  Haller,  and  by  numerous 
physiologists  who  have  since  investigated  this  subject,  and 
see  how  far  this  view  of  the  independence  of  the  contractile 
power  of  the  heart  accords  with  the  present  state  of  our 
knowledge. 

Experiments  have  shown  that  the  heart  will  pulsate  for  a 
time  when  removed  from  all  connection  with  other  parts  of 
the  organism.2  In  the  cold-blooded  animals,  in  which  the 
irritability  of  the  tissues  remains  for  some  time  after  death, 
this  is  particularly  marked.  It  is  not  the  blood  in  the  cavi- 
ties of  the  heart  which  causes  it  to  contract,  for  it  will  pul- 
sate when  its  cavities  have  been  'emptied.  It  is  not  the  con- 


1  HALLER,  Memoires  sur  la  Nature  Sensible  et  Irritable  des  Parties  du  Corps 
Animal,  Lausanne,  1756,  tome  i.     These  views  with  regard  to  the  cause  of  the 
action  of  the  heart  were  first  advanced  by  Haller  in  1739  in  commentaries  on  the 
"  Institutes  "  of  Boerhaave  (Mem.  de  HALLER,  p.  87). 

2  Numerous  instances  of  contractions  of  the  heart  in  cold-blooded  animals  con- 
tinuing for  a  very  long  time  after  excision,  are  on  record.     Dr.  Dunglison,  in  his 
work  on  Physiology  (op.  cit.,  vol.  i.,  p.  408),  mentions  several  instances  where  the 
heart  pulsated  for  from  ten  to  twenty-four  hours  after  removal  from  the  body. 
The  most  remarkable  examples  of  this  prolonged  action  were  in  the  heart  of  the 
sturgeon.    In  one  instance,  in  an  experiment  on  a  large  alligator,  we  found  the  heart 
pulsating,  in  situ,  twenty-eight  hours  after  the  animal  had  been  killed  by  the  injec- 
tion of  a  solution  of  woorara.      The  heart  was  then  excised,  and  continued  to 
beat  during  a  long  series  of  experiments,  until  it  was  arrested  by  powerful  compres- 
sion with  the  hand,  after  it  had  been  filled  with  water  and  the  vessels  tied. 


224:  CIRCULATION. 

tact  of  the  air,  for  the  heart  will  pulsate  in  a  vacuum.1  The 
heart  does  not  receive  its  irritability  from  the  nervous  sys- 
tem, for,  when  removed  from  the  body,  it  has  no  connection 
with  the  nervous  system ;  and  it  is  not  probable  that  it  re- 
ceives any  influence  from  sympathetic  ganglia  which  have 
lately  been  discovered  in  its  substance,  for  detached  portions 
of  the  heart  will  pulsate,  and  the  contractions  of  the  organ 
will  continue  in  animals  poisoned  with  woorara,  which  is 
known  to  paralyze  the  motor  system  of  nerves. 

It  is  unnecessary  to  refer  to  the  various  experiments 
which  have  demonstrated  the  independence  of  the  contrac- 
tions of  the  heart.  They  are  of  such  a  simple  nature  that  they 
may  be  verified  by  any  one  who  will  take  the  trouble  to  ex- 
cise the  heart  of  a  frog  or  turtle,  place  it  under  a  small  bell- 
glass  so  that  it  will  not  be  subject  to  possible  irritation  from 
currents  of  air,  and  watch  its  pulsations.  In  such  an  observa- 
tion as  this,  it  is  evident  that  for  a  certain  time  contractions, 
more  or  less  regular,  will  take  place ;  and  the  experiments 
referred  to  above  show  that  they  take  place  without  any  ex- 
ternal influence.  In  short,  it  is  evident  that  the  muscular 
fibres  of  the  heart  possess  an  irritability,  by  virtue  of  which 
they  will  contract  intermittently  for  a  time,  though  no  stim- 
ulus ~be  applied;  as  ordinary  striped  muscular  fibres  have  an 
irritability,  by  virtue  of  which  they  will  respond,  for  a  time, 
to  the  application  of  a  stimulus. 

It  is  manifestly  necessary  that  the  action  of  the  heart 
should  be  constant,  regular,  and  powerful ;  and  when  we  say 
that  the  irritability  inherent  in  its  muscular  tissue  is  such 
that  it  will  contract  for  a  time  without  any  external  stimulus, 
we  by  no  means  assume  that  this  is  the  cause  of  its  physiolog- 
ical action.  It  is  only  an  important  and  incontestable  prop- 
erty of  the  muscular  fibres  of  the  heart,  and  its  regular  action 
is  dependent  upon  other  circumstances. 

In  the  first  place,  we  have  to  inquire  what  makes  the  ac- 
tion of  the  heart  constant.  The  answer  to  this  is,  that  the 

1  JOHN  REID,  in  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  ii.,  p.  611. 


CAUSE  OF  THE  RHYTHMICAL  CONTRACTIONS  OF  THE  HEART.     225 

changes  of  nutrition,  by  which,  through  the  blood  circulating 
in  its  substance,  the  waste  of  its  tissue  is  constantly  supplied, 
preserves  the  integrity  of  the  fibres,  and  keeps  them,  conse- 
quently, in  a  condition  to  contract.  This  is  true,  likewise, 
of  the  ordinary  striped  muscular  fibres.  If  the  supply  of 
blood  be  cut  off  from  the  substance  of  the  heart,  especially  in 
the  warm-blooded  animals,  the  organ  soon  loses  its  irritabil- 
ity. This  was  beautifully  shown  by  the  experiments  of 
Erichsen.  This  observer,  after  exposing  the  heart  in  a  warm- 
blooded animal  and  keeping  up  artificial  respiration,  ligated 
the  coronary  arteries,  thus  cutting  off  the  greatest  part  of  the 
supply  of  blood  to  the  muscular  fibres.  He  found,  as  the 
mean  of  six  experiments,  that  the  heart  ceased  pulsating, 
though  artificial  respiration  wras  continued,  in  23^  minutes. 
After  the  pulsations  had  ceased,  they  could  be  restored  by 
removing  the  ligatures  and  allowing  the  blood  to  circulate 
again  in  the  substance  of  the  heart.1  The  same  is  true  of  the 
irritability  of  ordinary  muscles,  as  has  been  lately  shown  by 
the  experiments  of  Dr.  Brown-Sequard,  though  the  continu- 
ous action  of  the  heart  undoubtedly  causes  these  phenomena 
to  be  more  marked  and  rapid.  If  we  take  a  muscle  which 
has  just  lost  its  irritability  and  will  no  longer  respond  to  the 
most  powerful  stimulus,  and  inject  fresh  blood  by  the  artery 
supplying  it,  the  irritability  wrill  be  immediately  restored.8 

In  the  second  place,  the  regular  and  powerful  contraction 
of  the  Jieart  is  provided  foi*  l>y  the  circulation  of  the  blood 
through  its  cavities.  Though  the  heart,  removed  from  the 
body,  will  contract  for  a  time  without  a  stimulus,  it  can  be 
made  to  contract  during  the  intervals  of  repose  by  an  irri- 
tant, such  as  the  point  of  a  needle,  or  a  feeble  current  of  gal- 
vanism. For  a  certain  time  after  the  heart  has  ceased  to 
contract  spontaneously,  contractions  may  be  induced  in  this 
way.  This  can  easily  be  demonstrated  in  the  heart  of  any 

1  London  Medical  Gazette,  July  8,  1842.  - 

8  BROWN-SEQUARD,  Proprietes  et    Usages  du  sang   rouge  et  du  sang  noir,. 
Journal  de  la  Physiologic,  1858,  tome  i.,  p.  95  et  seq. 
15 


226  CIRCULATION. 

animal,  warm  or  cold-blooded.  This  irritability,  which  is 
manifested,  under  these  circumstances,  in  precisely  the  same 
way  as  in  ordinary  muscles,  is  different  in  degree  in  different 
parts  of  the  organ.  Haller  and  others  have  shown  that  it  is 
greater  in  the  cavities  than  on  the  surface ;  for  long  after  ir- 
ritation applied  to  the  exterior*fails  to  excite  contraction,  the 
organ  will  respond  to  a  stimulus  applied  to  its  interior.  The 
experiments  of  Haller  also  show  that  fluids  in  the  cavities  of 
the  heart  have  a  remarkable  influence  in  exciting  and  keep- 
ing up  its  contractions.  This  observation  is  of  much  interest, 
as  showing  conclusively  that  the  presence  of  blood  is  neces- 
sary to  the  natural  and  regular  action  of  the  heart.  "We 
quote  one  of  the  experiments  on  this  point  performed  upon  a 
cat: 

«  -x-  #  *  T^  superior  vena  cava  having  been  divid- 
ed, and  the  inferior  ligated,  and  the  pulmonary  artery  opened, 
and  the  right  ventricle  emptied  by  a  sufficient  compression, 
and  the  aorta  ligated,  all  with  promptitude,  I  saw  the  right 
auricle  repose  first,  the  right  ventricle  continued  to  beat  for 
some  time  in  unison  with  the  left  ventricle,  and  its  walls  de- 
scended toward  the  middle  line  of  the  heart :  but  this  ven- 
tricle did  not  delay  to  lose  its  movement  the  first.  As  for 
the  other  ventricle,  which  could  no  longer  empty  itself  into 
the  aorta,  it  was  filled  with  blood,  and  its  movement  contin- 
ued for  four  hours.  *  *  * 

This  experiment  was  confirmed  by  numerous  others.  It 
will  be  observed  that  one  side  of  the  heart  was  made  to  cease 
its  pulsations,  while  the  other  side  continued  to  contract,  by 
simply  removing  the  blood  from  its  interior ;  which  conclu- 
sively proves  that,  though  the  heart  may  act  for  a  time  in- 
dependently, the  presence  of  blood  in  its  cavities  is  a  stim- 
ulus capable  of  prolonging  its  regular  pulsations.  Schiff  has 
gone  still  further,  and  succeeded  in  restoring  the  pulsations 
in  the  heart  of  a  frog,  which  had  ceased  after  it  had  been 

1  HALLER,  Memoircs  sur  la  Nature  Irritable  et  Sensible  des  Parties,  etc.,  tome 
i.,  p.  363. 


CAUSE  OF  THE  RHYTHMICAL  CONTRACTIONS  OF  THE  HEART.    227 

emptied,  by  introducing  a  few  drops  of  blood  into  the  au- 
ricle.1 Our  own  experiments  upon  the  hearts  of  alligators 
and  turtles  show  that  when  removed  from  the  body  and 
emptied  of  blood,  the  pulsations  are  feeble,  rapid,  and  irreg- 
ular ;  but  that  when  filled  with  blood,  the  valves  being  de- 
stroyed so  as  to  allow  free  passage  in  both  directions  between 
the  auricles  and  ventricle,  the  contractions  become  powerful 
and  regular.  In  these  experiments,  when  water  was  intro- 
duced instead  of  blood,  the  pulsations  became  more  regular 
but  were  more  frequent  and  not  as  powerful  as  when  blood 
was  used.2  These  experiments  show  also  that  the  action  of 
the  heart  may  be  affected  by  the  character,  particularly  the 
density,  of  the  fluid  which  passes  through  it,  which  may  ex- 
plain its  rapid  and  feeble  action  in  anemia. 

It  seems  wrell  established  that  the  heart,  though  capable 
of  independent  action,  is  excited  to  contraction  by  the  blood 
as  it  passes  through  its  cavities.  A  glance  at  the  succession 
of  its  movements,  particularly  in  the  cold-blooded  animals, 
where  they  are  so  slow  that  the  phenomena  can  be  easily  ob- 
served, will  show  how  these  contractions  are  induced.  If  we 
look  at  the  organ  as  it  is  in  action,  we  see  first  a  disten- 
tion  of  the  auricle ;  this  is  immediately  followed  by  a  con- 
traction filling  the  ventricle,  which  in  its  turn  contracts. 
Undoubtedly  the  tension  of  the  fibres,  as  well  as  the  contact 
of  blood  in  its  interior,  acts  as  a  stimulus ;  and  as  all  the 
fibres  of  each  cavity  are  put  on  the  stretch  at  the  same  in- 
stant, they  contract  simultaneously.  The  necessary  regular 
distentionof  each  cavity  thus  produces  rhythmical  and  forcible 
contractions ;  and  the  mere  fact  that  the  action  of  the  heart 
alternately  empties  and  dilates  its  cavities,  insures  regular 
pulsations  as  long  as  blood  is  supplied,  and  no  disturbing  in- 
fluences are  in  operation. 

The  muscular  fibres  of  the   heart   are    endowed  with 

1  MILNE-EDWARDS,  op.  cit.,  tome  iv.,  p.  126. 

2  Action  of  tlie  Heart  and  Respiration,  American  Journal  of  the  Medical 
Sciences,  Oct.   1861. 


228  CIRCULATION. 

an  inherent  property,  called  irritability,  by  virtue  of  which 
they  will  contract  for  a  certain  time  without  the  application 
of  a  stimulus.  Irritability,  manifested  in  this  way,  continues 
so  long  as,  by  the  processes  of  nutrition,  the  fibres  are  main- 
tained in  their  integrity.  The  muscular  tissue,  however,  may 
be  thrown  into  contraction,  dufing  the  intervals  of  repose,  by 
the  application  of  a  stimulus,  a  property  which  is  enjoyed 
by  all  muscular  fibres.  The  irritability  manifested  in  this 
way  is  much  more  marked  in  the  interior  than  on  the  exterior 
of  the  organ.  Blood  in  contact  with  the  lining  membrane  of 
the  heart  acts  as  a  stimulus  in  a  remarkable  degree,  and  is 
even  capable  of  restoring  irritability  after  it  has  become  ex- 
tinct. The  passage  of  blood  through  the  heart  is  the  natural 
stimulus  of  the  organ,  and  may  be  said  to  be  the  cause  of 
its  regular  pulsations,  though  it  by  no  means  endows  the 
fibres  with  their  contractile  properties. 


Influence  of  the  Nervous  System  on  the  Heart. 

The  movements  of  the  heart,  as  we  have  seen,  are  not 
directly  under  the  control  of  the  will ;  and  observations  on 
the  human  subject,  as  well  as  on  living  animals,  have  shown 
that  the  organ  is  devoid  of  general  sensibility.  The  latter 
fact  was  demonstrated  in  the  most  satisfactory  manner  by  Har- 
vey in  the  case  of  the  Yiscount  Montgomery.  In  this  case 
the  heart  was  exposed  ;  and  Harvey  found  that  it  could  be 
touched  and  handled  without  even  the  knowledge  of  the  sub- 
ject. This  has  been  verified  in  other  instances  in  the  human 
subject.  Its  physiological  movements  are  capable  of  being 
influenced  in  a  remarkable  degree  through  the  nervous  sys- 
tem, notwithstanding  this  insensibility,  and  in  spite  of  the 
fact  that  the  muscular  fibres  composing  it  are  capable  of 
contraction  when  removed  from  all  connection  with  the 
body,  and  that  the  regular  pulsations  can  be  kept  up  for  a 
long  time  "by  the  mere  passage  of  blood  through  its  cavities. 
The  influence  thus  exerted  is  so  great,  that  some  eminent  au- 


INFLUENCE   OF   THE   NEEVOTJS    SYSTEM   ON   THE    HEART.    229 

thorities  held  the  opinion  that  the  cause  of  the  irritability  of 
the  organ  was  derived  from  the  nerves.  One  of  the  most 
distinguished  advocates  of  this  opinion  was  Legallois.  This 
observer  arrested  the  action  of  the  heart  of  the  rabbit  by  sud- 
denly destroying  the  spinal  cord,  from  which  he  drew  the 
conclusion  that  the  heart  derived  its  contractile  power  from 
the  cerebro-spinal  system.1  The  experiments  which  we  have 
already  cited,  showing  the  continuance  of  the  heart's  action 
after  excision,  disprove  this  so  completely,  that  it  was  not 
thought  worth  while  to  discuss  this  view  while  treating  of 
the  cause  of  its  rhythmical  contraction.  The  same  may  be 
said  with  regard  to  the  experiments  of  Brachet,  in  which  he 
endeavored  to  prove  that  the  contractility  of  the  heart  is  de- 
rived from  the  cardiac  plexus  of  the  sympathetic  system  of 
nerves.  The  fact  that  the  heart  does  not  depend  for  its  con- 
tractility upon  external  nervous  influence  may  be  regarded 
as  long  since  definitely  settled  ;  but  within  a  few  years  the 
discovery  in  its  substance  of  ganglia  belonging  to  the  sympa- 
thetic system  has  revived,  to  some  extent,  the  view  that  its 
irritability  is  derived  from  nerves. 

It  is  not  necessary  to  follow  out  all  the  experiments  which 
combine  to  demonstrate  the  incorrectness  of  this  view.  Ber- 
nard, by  a  series  of  admirably  conceived  experiments  upon 
the  effects  of  the  woorara  poison,  has  succeeded  in  demon- 
strating the  distinction  between  muscular  and  nervous  irri- 
tability.2 In  an  animal  killed  with  this  remarkable  poison, 
the  functions  of  the  motor  nerves  are  entirely  abolished ;  so 
that  galvanization,  or  other  irritation,  does  not  produce  the 
slightest  effect.  Yet  the  muscles  retain  their  irritability,  and 
if  artificial  respiration  be  kept  up,  the  circulation  will  con- 
tinue for  a  long  time.  The  heart,  by  this  means,  seems  to 
be  isolated  from  the  nervous  system  as  completely  as  if  it  were 
excised;  and  galvanization  of  the  pneumogastric  nerves  in 

1  LEGALLOIS,  (Euvres,  tome  i.,  p.  97. 

BERNARD,  Lemons  sur  les  Effete  des  Substances  Toxiques  el  Medicamen  femes, 
Paris,  1857. 


230  CIRCULATION. 

the  neck,  which,  in  a  living  animal,  will  immediately  arrest 
its  action,  has  no  effect.  On  the  other  hand,  poisoning  by 
the  sulpho-cyanide  of  potassium  destroys  the  muscular  irrita- 
bility, and  leaves  the  nerves  intact.  By  these  experiments, 
which  we  have  frequently  repeated,  we  can  completely  sep- 
arate the  nervous  from  the  rSuscular  irritability,  and  show 
their  entire  independence  of  each  other ;  and  there  is  every 
reason  to  suppose  that  the  heart,  like  the  other  muscles,  does 
not  derive  its  contractility  from  any  other  system. 

It  is  evident,  however,  that  the  heart  is  often  powerfully 
influenced  through  the  nerves.  Sudden  and  violent  emotions 
will  occasionally  arrest  its  action,  and  have  been  known  to 
produce  death.  Palpitations  are  to  be  accounted  for  in  the 
same  way.  Some  of  the  modifications  which  we  have  already 
considered,  depending  on  exercise,  digestion,  etc.,  are  effected 
through  the  nerves ;  and  it  is  through  this  system  that  the 
heart,  and  all  the  important  organs  of  the  body,  are  made  to 
a  certain  extent  mutually  dependent.  It  becomes  interesting, 
and  highly  important,  then,  to  study  their  influences,  and 
follow  out,  as  clearly  as  possible,  the  action  of  the  nerves 
which  are  distributed  to  the  heart. 

The  anatomical  connections  of  the  heart  with  the  nervous 
centres  are  mainly  through  the  sympathetic  and  the  pneu- 
mogastric  nerves.  We  can  study  the  influence  of  these  nerves 
to  most  advantage  in  two  ways :  first,  by  dividing  them  and 
watching  the  effect  of  depriving  the  heart  of  their  influence ; 
and  second,  by  exciting  them  by  means  of  a  feeble  current 
of  galvanism.  It  is  well  known  that  in  an  animal  just  killed 
the  "  nervous  force  "  may  be  closely  imitated  by  galvanism, 
which  is  better  than  any  other  means  of  stimulation,  as  it 
does  not  affect  the  integrity  of  the  nerves,  and  the  amount 
of  the  irritation  may  be  easily  regulated.1 

1  We  shall  not  discuss  the  effects  upon  the  heart  of  sudden  destruction  of  the 
great  nervous  centres.  It  has  been  shown  that  the  heart  becomes  arrested  when 
the  brain  is  crushed,  as  by  a  blow  with  a  hammer,  when  the  medulla  oblongata  or 
the  spinal  cord  is  suddenly  destroyed ;  and  even  the  crushing  of  a  foot,  in  the  frog. 


DIVISION   OF  THE  PNEUMOGASTRIC8.  231 

Experiments  on  the  influence  of  the  sympathetic  nerves 
upon  the  heart  are  not  quite  as  satisfactory  as  we  might 
desire.  Brachet  asserts  that  the  action  of  the  heart  is  imme- 
diately arrested  by  destroying  the  cardiac  plexus.1  With 
regard  to  this  observation,  we  must  take  into  account  the 
difficulty  of  making  the  operation,  and  the  disturbance  of  the 
heart  consequent  upon  the  necessary  manipulations  ;  circum- 
stances which  take  away  much  of  its  value.  It  has  been 
shown  pretty  conclusively,  however,  that  stimulation  of  the 
sympathetic  in  the  neck  has  the  effect  of  accelerating  the 
pulsations  of  the  heart.2  The  extreme  difficulty  of  dividing 
all  the  branches  of  the  sympathetic  going  to  the  organ  leaves 
a  doubt  as  to  whether  such  an  operation  would  definitely 
abridge  its  action. 

We  have  next  to  consider  the  influence  of  the  pneumo- 
gastrics  upon  the  heart.  Experiments  on  these  nerves  are 
made  with  greater  facility  than  on  the  nerves  of  the  sympa- 
thetic system,  and  the  results  are  much  more  satisfactory. 
Like  all  the  cerebro-spinal  nerves,  the  influence  generated 
in  the  nervous  centre  from  which  they  take  their  origin 
is  conducted  along  the  nerve,  and  manifested  at  its  distribu- 
tion. When  they  are  divided,  we  may  be  sure  that,  as  far 
as  they  are  concerned,  all  the  organs  which  they  supply 
are  cut  off  from  nervous  influence ;  and  when  galvanized  in 
their  course,  we  imitate  or  exaggerate  the  influence  sent  from 
the  nervous  centre. 

The  invariable  effect  on  the  heart  of  division  of  the  pneu- 
mogastric  nerves  in  the  neck  is  an  increase  in  the  frequency, 
and  diminution  in  the  force,  of  its  pulsations.  One  or  two 

has  been  known  to  produce  this  effect.  In  fine,  this  may  be  done  by  any  exten- 
sive injury  to  the  nervous  system ;  but  this  fact  does  not  teach  us  much  with 
regard  to  the  physiological  influences  of  the  nerves.  For  example,  while  crush- 
ing of  the  brain  arrests  the  heart,  the  brain  may  be  removed  from  a  living  animal, 
and  the  heart  will  beat  for  days.  Experiments  upon  the  influence  of  the  medulla 
oblongata  and  spinal  cord  are  by  no  means  satisfactory. 

1  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  ii.,  p.  612. 

3  MILNE-EDWARDS,  Physiologic,  tomeiv.,  p.  156,  note. 


232  CIRCULATION. 

writers  have  denied  this  fact,  but  it  is  confirmed  bj  the  testi- 
mony of  nearly  all  experimenters.  To  anticipate  a  little  in 
the  history  of  the  pneumogastric  nerves,  it  may  be  stated  that 
while  they  are  exclusively  sensitive  at  their  origin,  they  receive 
after  having  emerged  from  the  cranial  cavity  a  number  of 
filaments  from  various  motor  tierves.  That  they  influence 
certain  muscles,  is  shown  by  their  paralysis  after  division  of 
the  nerves  in  the  neck;  as,  for  example,  the  arrest  of  the 
movements  of  the  glottis. 

Having  this  double  property  of  motion  and  sensation,  and 
being  distributed  in  part  to  an  organ  composed  almost  exclu- 
sively of  muscular  fibres,  which,  as  we  have  seen,  is  not  en- 
dowed with  general  sensibility,  we  should  expect  that  their 
section  would  arrest,  or  at  least  diminish,  the  frequency  of 
the  heart's  action.  "What  explanation,  then,  can  we  offer  for 
the  fact  that  this  seems  actually  to  excite  the  movements 
of  the  heart?  We  will  be  better  prepared  to  answer  this 
question  after  we  have  studied  the  effects  of  galvanization  of 
the  nerves  in  a  living  animal,  or  one  in  which  the  action  of 
the  heart  is  kept  up  by  artificial  respiration. 

Numerous  experiments  have  been  made  with  reference  to 
the  effects  on  the  heart  of  galvanic  currents,  both  feeble  and 
powerful,  passed  through  the  pneumogastrics  before  division, 
of  currents  passed  through  the  upper  and  lower  extremities 
after  division,  etc.,  a  full  detail  of  which  belongs  properly  to 
the  physiological  history  of  the  nervous  system.  In  this  con- 
nection, a  few  of  these  facts  only  need  be  stated. 

It  has  been  shown  by  repeated  experiments,  which  we 
have  frequently  confirmed,  that  a  moderately  powerful  cur- 
rent of  galvanism  passed  through  both  pneumogastrics  will 
arrest  the  action  of  the  heart,  and  that  the  organ  will  cease 
its  contractions  as  long  as  the  current  is  continued.  This 
experiment  has  been  performed  upon  living  animals,  both 
with  and  without  exposure  of  the  heart.  The  arrest  is  not 
due  to  violent  and  continued  contraction  of  the  muscular 
fibres ;  on  the  contrary,  the  heart  is  relaxed,  its  ventricles  are 


GALVANIZATION   OF  THE  PNEUMOGASTKICS.  233 

flaccid,  and  its  fibres  are  for  the  time  paralyzed.  The  ques- 
tion then  arises  whether  this  action  is  directly  exerted  on  the 
heart  through  the  nerves,  or  whether  an  influence  is  conveyed 
to  the  nervous  centre,  and  transmitted  to  the  heart  in  another 
way.  This  is  settled  by  the  experiment  of  dividing  the 
nerves  and  galvanizing  alternately  the  extremities  connected 
with  the  heart  and  those  connected  with  the  nervous  centres. 
It  has  been  ascertained  that  galvanization  of  the  extremities 
connected  with  the  heart  arrests  its  action,  while  galvaniza- 
tion of  the  central  extremities  has  no  such  effect.  Another 
interesting  fact  also  shows  that  the  influence  exerted  upon 
the  heart  is  through  the  motor  filaments  of  the  pneumogas- 
trics.  It  has  been  shown  by  Bernard,  in  a  very  curious  series 
of  experiments  which  we  will  not  fully  discuss  in  this  connec- 
tion, that  the  woorara  poison  paralyzes  only  the  motor  nerves, 
leaving  the  sensory  nerves  intact.  If  we  expose  the  heart 
and  pneumogastric  nerves  in  a  warm-blooded  animal  poi- 
soned with  this  agent,  and  continue  the  pulsations  by  keep- 
ing up  artificial  respiration,  we  find  that  the  most  powerful 
current  of  galvanism  passed  through  the  pneumogastrics  has 
no  effect  upon  the  heart.  The  effect  of  a  feeble  current  of 
galvanism  upon  the  motor  nerves  is  so  like  the  operation  of 
the  natural  stimulus,  or  nervous  force,  that  for  a  time  many 
physiologists  regarded  the  two  forces  as  identical.  Though 
this  view  is  not  received  at  the  present  day,  it  is  an  admitted 
fact  that  by  galvanism  we  imitate  in  the  closest  manner  the 
natural  action  of  the  motor  nerves,  and  this  has  become  a 
most  valuable  means  of  investigation  into  the  physiology  of 
the  nervous  system. 

Though  galvanization  of  the  pneumogastrics  arrests  the 
action  of  the  heart  in  nearly  all  animals,  there  are  some  in 
which  this  does  not  take  place,  as  in  birds ;  a  fact  which  is 
stated  by  Bernard,1  but  for  which  he  offers  no  explanation. 
In  some  experiments  instituted  on  this  subject  a  few  years 

1  BERNARD,  Physiologic  et  Pathologie  du  Systeme  J!Wv<?wa;,Paris,  1858,  tome  iL, 
p.  394. 


234  CIRCULATION. 

ago  on  alligators,  we  noticed  a  singular  peculiarity  which 
throws  some  light  on  the  question  we  are  now  considering. 
Desiring  to  demonstrate  to  the  class  at  the  New  Orleans 
School  of  Medicine  the  action  of  the  heart  in  this  animal,  an 
alligator  six  feet  in  length  was  poisoned  with  woorara,  and 
the  heart  exposed.  The  animal  came  under  the  influence  of 
the  poison  in  about  thirty  minutes,  when  the  dissection  was 
commenced,  and  was  quite  dead  when  the  heart  was  exposed. 
The  pneumogastrics  were  then  exposed  and  galvanized,  with 
the  effect  of  promptly  arresting  the  action  of  the  heart.  This 
observation  was  verified  in  another  experiment.  "We  were 
at  first  at  a  loss  to  account  for  the  absence  of  effect  of  the 
woorara  on  the  motor  filaments  of  the  pneumogastric  nerves ; 
but  on  reflection  thought  it  might  be  due  to  slow  absorption  of 
the  poison  in  so  large  a  cold-blooded  animal.  With  a  view 
of  ascertaining  whether  there  is  any  difference  in  the  prompt- 
ness with  which  different  nerves  in  the  body  are  affected  by 
this  agent,  we  made  the  following  experiment  upon  a  dog. 
The  animal  was  brought  under  the  influence  of  ether,  and 
the  heart,  the  pneumogastrics,  and  the  sciatic  nerve  were 
exposed.  Galvanization  of  the  sciatic  produced  muscular 
contraction,  and  of  the  pneumogastrics  arrested  the  heart 
promptly.  A  grain  of  woorara,  dissolved  in  water,  was  then 
injected  under  the  skin  of  the  thigh.  One  hour  after  the 
injection  of  the  woorara,  the  sciatic  was  found  insensible  to 
galvanism,  but  the  heart  could  be  arrested  by  galvanization 
of  the  pneumogastrics,  though  it  required  a  powerful  current. 
A  weaker  current  diminished  the  frequency,  and  increased 
the  force,  of  its  pulsations.1  In  this  experiment,  the  opera- 
tion of  opening  the  chest  undoubtedly  diminished  the  activity 
of  absorption  of  the  poison,  and  consequently  retarded  its  ef- 
fects upon  the  nervous  system.  Taken  in  connection  with 

1  This  increase  in  the  'force  of  the  heart,  which  accompanied  the  diminution  in 
the  frequency  of  its  pulsations,  consequent  upon  feeble  galvanization  of  the  pneu- 
mogastrics, was  constantly  observed  in  many  experiments.  The  force  of  the  pul- 
sations was  measured  by  the  cardiometer. 


GALVANIZATION   OF   THE   PNEUMOGASTRICS.  235 

the  observations  on  alligators,  it  shows  that  the  motor  nerves 
are  not  all  affected  at  the  same  time,  and  that  the  pneumo- 
gastrics  resist  the  action  of  this  peculiar  poison  after  the 
motor  nerves  generally  are  paralyzed.  This  shows  a  conser- 
vative provision  of  Nature  which  guards  particularly  the  im- 
portant influence  exerted  by  these  nerves  upon  the  heart.1 

Our  knowledge  of  the  inherent  properties  of  the  muscular 
fibres  of  the  heart,  and  the  effects  of  the  passage  of  blood 
through  its  cavities,  which  together  are  competent  to  keep 
up  for  a  time  regular  pulsations  without  the  intervention  of 
the  nervous  system,  taken  in  connection  with  the  facts  just 
stated,  concerning  the  influence  of  section  or  galvanization 
of  the  pneumogastric  nerves,  enables  us  to  comprehend  pretty 
well  the  influence  of  these  nerves  on  the  heart.  They  un- 
doubtedly perform  the  important  function  of  regulating  the 
force  and  frequency  of  its  pulsations. 

Hardly  any  reflection  is  necessary  to  convince  us  of  the 
importance  of  such  a  function,  and  how  it  must  of  necessity 
be  accomplished  through  the  pneumogastrics.  It  is  impor- 
tant, of  course,  that  the  heart  should  act  at  all  times  with 
nearly  the  same  force  and  frequency.  We  have  seen  that 
the  inherent  properties  of  its  fibres  are  competent  to  make  it 
contract,  and  the  necessary  intermittent  dilitation  of  its  cavi- 
ties makes  these  contractions  assume  a  certain  regularity ; 
but  the  quantity  and  density  of  the  blood  are  subject  to  very 
considerable  variations  within  the  limits  of  health,  which, 
without  some  regulating  influence,  would  undoubtedly  cause 
variations  in  the  heart's  action,  so  considerable  as  to  be  inju- 
rious. This  is  shown  by  the  comparatively  inefficient  and 
palpitating  action  of  the  heart  when  the  pneumogastrics  are 
divided.  These  nerves  convey  to  the  heart  a  constant  influ- 
ence, which  we  may  compare  to  the  insensible  tonicity  im- 
parted to  voluntary  muscles  by  the  general  motor  system. 

1  For  details  of  these  experiments  the  reader  is  referred  to  an  article  by  the 
author,  on  the  Action  of  the  Heart  and  Respiration,  in  The  American  Journal  of 
Medical  Sciences,  Oct.,  1861. 


236  CIRCULATION. 

For  we  know  that  when  a  set  of  muscles  on  one  side  is  par- 
alyzed, as  in  facial  palsy,  their  tonicity  is  lost,  they  become 
flaccid,  and  the  muscles  on  the  other  side,  without  any  effort 
of  the  will,  distort  the  features. 

"We  can  imitate  an  exaggeration  of  this  force  by  a  feeble 
current  of  galvanism,  which  makes  the  pulsations  of  the  heart 
less  frequent  and  more  powerful ;  or  exaggerate  it  still  more 
by  a  more  powerful  current,  which  arrests  the  action  of  the 
heart  altogether. 

Phenomena  are  not  wanting  in  the  human  subject  which 
verify  these  views.  Causes  which  operate  through  the 
nervous  system  frequently  produce  palpitation  and  irregular 
action  of  the  heart.  Cases  are  not  uncommon  in  which  pal- 
pitation habitually  occurs  after  a  full  meal.  There  are  in- 
stances on  record  of  immediate  death  from  arrest  of  the 
heart's  action  from  fright,  anger,  grief,  or  other  severe  men- 
tal emotions.  Syncope  from  these  causes  is  by  no  means  un- 
common. In  the  latter  instance,  when  the  heart  resumes  its 
functions,  the  nervous  shock  carried  along  the  pneumogastrics 
is  only  sufficient  to  arrest  its  action  temporarily.  When 
death  takes  place,  the  shock  is  so  great  that  the  heart  never 
recovers  from  its  effects.1 


Summary  of  certain  Causes  of  Arrest  of  the  Action  of  the 
^c  Heart. 

In  warm-blooded  animals,  the  heart's  action  speedily 
ceases  after  it  is  deprived  of  its  natural  stimulus,  the  blood. 
It  is  not  from  experiments  on  the  inferior  animals  alone  that 
we  derive  proof  of  this  fact.  It  is  well  known  that  in  profuse 
hemorrhage  in  the  human  subject,  the  contractions  of  the 

1  An  explanation  of  the  influence  of  the  pneumogastric  nerves  on  the  heart, 
very  like  the  one  we  have  given,  is  made  by  Longet  (Traite  de  Physiologic, 
Paris,  1861,  tome  i.,  p.  785);  but  this  author  assumes  that  the  pneumogastrics 
and 'the  sympathetic  have  an  antagonistic  action,  the  former  moderating,  and  the 
latter  accelerating  the  heart's  action. 


CAUSES   OF   ARREST   OF   THE    ACTION    OF   THE    HEART.        237 

heart  are  progressively  enfeebled,  and,  when  the  loss  of  blood 
has  proceeded  to  a  certain  extent,  are  permanently  arrested. 
Cases  of  transfusion  after  hemorrhage  show  that  when  blood 
is  introduced,  the  heart  may  be  made  to  resume  its  pulsa- 
tions. The  same  result  takes  place  in  death  by  asthenia ;  and 
cases  are  on  record  where  life  has  been  prolonged,  as  in  hem- 
orrhage, by  transfusion  of  even  a  small  quantity  of  healthy 
blood.  These  facts  have  been  demonstrated  on  the  inferior 
animals  by  experiments  already  cited.  The  experiment  of 
Haller,  in  which  the  action  of  the  right  side  of  the  heart  of  a 
cat  was  arrested  by  emptying  it  of  blood,  while  the  left  side, 
which  was  filled  with  blood,  coDtinued  to  pulsate,  showed 
that  the  absence  of  blood  in  its  cavities  is  competent  of  itself 
to  arrest  the  heart.  The  experiments  of  Erichsen,  who  par- 
alyzed the  heart  by  ligating  the  coronary  arteries,  and  Schiff, 
who  produced  a  local  paralysis  by  ligating  the  vessel  going  to 
the  right  ventricle,  show  that  the  heart  may  also  be  arrested 
by.  cutting  off  the  circulation  of  blood  in  its  substance.  Both 
of  these  causes  must  operate  in  arrest  of  the  heart's  action 
in  hemorrhage. 

The  mechanical  causes  of  arrest  of  the  heart's  action  are 
of  considerable  pathological  importance.  The  heart,  in 
common  with  other  muscles,  may  be  paralyzed  by  sufficient 
mechanical  injury.  A  violent  blow  upon  the  deltoid  paralyzes 
the  arm ;  a  severe  strain  will  paralyze  the  muscles  of  an 
extremity ;  in  the  same  way  excessive  distention  of  the  cav- 
ities of  the  heart  will  arrest  its  pulsations.  This  is  shown  by 
arrest  of  the  circulation  in  asphyxia.  "We  have  already  seen, 
that  under  these  circumstances  the  heart  is  incapable  of 
forcing  the  unaerated  blood  through  the  systemic  capillaries ; 
it  finally  becomes  enormously  strained  and  distended,  and 
consequently  paralyzed.  The  same  result  follows  the  appli- 
cation of  a  ligature  to  the  aorta.  This  effect  may  be  pro- 
duced, also,  in  the  cold-blooded  animals,  in  which,  if  the 
heart  be  left  undisturbed,  the  pulsations  will  continue  for  a 
long  time.  The  following  experiment  illustrating  this  point 


238  CIRCULATION. 

was  performed  upon  the  heart  of  an  alligator  six  feet  in 
length : 

The  animal  was  poisoned  with  woorara,  and  twenty-eight 
hours  after  death  the  heart,  which  had  been  exposed  and  left 
in  situ,  was  pulsating  regularly.  It  was  then  removed  from 
the  body,  and  after  some  experiments  on  the  comparative 
force,  etc.,  of  the  pulsations,  when  empty,  and  when  filled 
with  blood,  was  filled  with  water,  the  valves  having  been 
destroyed  so  as  to  allow  free  passage  of  the  fluid  through  the 
cavities,  and  the  vessels  ligated.  "  TJie  ventricles,  still  filled 
with  water  confined  in  their  cavity,  were  then  firmly  com- 
pressed with  the  hand,  so  as  to  subject  the  muscular  fibres  to 
powerful  compression.  From  that  time  the  heart  entirely 
ceased  its  contractions,  and  became  hard,  like  a  muscle  in  a 
state  of  cadaveric  rigidity."  ] 

This  experiment  shows  how  completely  and  promptly  the 
heart,  even  of  a  cold-blooded  animal,  may  be  arrested  in  its 
action  by  mechanical  injury. 

Cases  of  death  from  distention  of  the  heart  are  not  infre- 
quent in  practice.  It  is  well  established  that  the  form  of 
organic  disease  which  most  frequently  leads  to  sudden  death 
is  that  in  which  the  heart  is  liable  to  great  distention.  "We 
refer  to  disease  at  the  aortic  orifice.  In  other  lesions,  there 
is  not  this  tendency  ;  but  when  the  aortic  orifice  is  contracted, 
or  the  valves  are  insufficient,  any  great  disturbance  of  the 
circulation  will  cause  the  heart  to  become  engorged,  which  is 
liable  to  produce  a  fatal  result. 

Most  persons  are  practically  familiar  with  the  distress- 
ing sense  of  suffocation  which  frequently  follows  a  blow 
upon  the  epigastrium.  A  few  cases  are  on  record  of  instan- 
taneous death  following  a  comparatively  slight  blow  in  this 
region.  We  had  an  opportunity  in  the  winter  of  1854-'55  of 
witnessing  an  autopsy  in  a  case  of  this  kind.  A  young 
mulatto  man,  employed  as  a  waiter  at  the  Louisville  Hotel, 
received  a  blow  in  the  epigastrium,  while  frolicking,  which 

1  American  Journal,  Oct.  1861,  p.  352. 


CAUSES    OF    ARREST   OF   THE   ACTION    OF   THE    HEART.      239 

produced  instantaneous  death.  On  post-mortem  examination 
no  lesion  was  discovered.  Though  these  cases  are  rare,  they 
are  well  known,  and  the  effects  are  generally  attributed  to 
injury  of  the  solar  plexus.  The  distress  is  precisely  what 
would  occur  from  sudden  arrest  of  the  heart's  action ;  for  it 
is  the  blood  charged  with  oxygen  and  sent  by  the  heart  to 
the  system,  which  supplies  the  wants  of  the  tissues,  and  not 
the  simple  entrance  of  air  into  the  lungs;  and  arrest  of  the 
circulation  of  arterial  blood,  from  any  cause,  produces  suffo- 
cation as  completely  as  though  the  trachea  were  ligated. 
This  fact  is  clearly  proven  by  experiments  in  the  article  re- 
ferred to  above.  It  is  a  question  whether  the  arrest  of  the 
heart,  if  this  be  the  pathological  condition,  be  due  to  concus- 
sion of  the  nervous  centre,  or  to  the  direct  effects  of  the  blow 
upon  the  organ  itself.  Our  present  data  do  not  enable  us  to 
answer  this  question  definitely,  but  rather  incline  us  to  the 
opinion  that  in  such  accidents  the  symptoms  are  due  to  direct 
injury  of  the  heart.  An  additional  argument  in  favor  of  this 
view  is  founded  on  our  knowledge  of  the  mode  of  operation 
of  the  sympathetic  system.  The  effects  of  stimulation  or 
irritation  of  this  system  are  not  instantaneously  manifested, 
as  is  the  case  in  the  cerebro-spinal  system,  but  are  developed 
slowly  and  gradually. 

As  far  as  we  have  been  able  to  learn  by  experiment,  the 
nervous  influences  which  arrest  the  action  of  the  heart  oper- 
ate through  the  pneumogastrics.  As  we  have  just  seen,  we 
can  closely  imitate  this  action  by  galvanism.  The  causes  of 
arrest  in  this  way  are  numerous.  Among  them  may  be  men- 
tioned, sudden  and  severe  bodily  pain  and  severe  mental 
emotions.  With  the  exceptions  of  arrest  of  the  heart  from 
loss  of  blood  and  from  distention,  from,  whatever  cause  it  may 
occur,  stoppage  of  the  heart  takes  place  through  the  nervous 
system.  It  may  be  temporary,  as  in  syncope,  or  it  may  be 
permanent ;  examples  of  which,  though  rare,  are  sufficiently 
well  authenticated. 


CHAPTEE  VI. 

CIRCULATION    OF   THE    BLOOD   IN   THE   ARTERIES. 

Physiological  anatomy  of  the  arteries — Course  of  blood  in  the  arteries — Elasticity 
of  the  arteries — Contractility  of  the  arteries — Locomotion  of  the  arteries  and 
production  of  the  pulse — Form  of  the  pulse — Sphygmograph — Pressure  of 
blood  in  the  arteries — Hemodynamometer — Cardiometer — Differential  cardio- 
meter — Pressure  in  different  parts  of  the  arterial  system — Influence  of  respi- 
ration on  the  arterial  pressure — Effects  of  hemorrhage — Rapidity  of  the  cur- 
rent of  blood  in  the  arteries — Instruments  for  measuring  the  rapidity  of  the 
arterial  circulation — Variations  in  rapidity  with  the  action  of  the  heart — Ra- 
pidity in  different  parts  of  the  arterial  system — Arterial  murmurs. 

IN  man  and  in  all  animals  possessed  of  a  double  heart, 
each  contraction  of  this  organ  forces  a  charge  of  blood  from 
the  right  ventricle  into  the  pulmonary  artery,  and  from  the 
left  ventricle  into  the  aorta.  We  have  seen  how  the  valves 
which  guard  the  orifices  of  these  vessels  effectually  prevent 
regurgitation  during  the  intervals  of  contraction.  There  is, 
therefore,  but  one  direction  in  which  the  blood  can  flow  in 
obedience  to  this  intermittent  force ;  and  the  fact  that  in  the 
smallest  arteries  there  is  an  acceleration  in  the  current  coin- 
cident with  each  contraction  of  the  heart,  which  disappears 
when  the  action  of  the  heart  is  arrested,  shows  that  the  ven- 
tricular systole  is  the  prime  cause  of  the  arterial  circulation. 

This  part  of  the  physiology  of  the  circulation  is  not  as 
simple  as  we  might  at  first  be  led  to  suppose.  The  arteries 
have  the  important  function  of  supplying  nutritive  matter  to 
all  the  tissues,  of  furnishing  to  the  glands  materials  out  of 


PHYSIOLOGICAL   ANATOMY   OF   THE   AKTEEIES.  241 

which  the  secretions  are  formed,  and  in  short  are  the  avenues 
of  supply  to  every  part  of  the  organism.  The  supply  of 
blood  regulates,  to  a  considerable  extent,  the  process  of  nu- 
trition, and  has  an  important  bearing  on  the  general  and 
special  functions.  The  physiological  processes  necessarily 
demand  considerable  modifications  in  the  quantity  of  arterial 
blood  which  is  furnished  to  parts  at  different  times.  For  ex- 
ample, during  secretion,  the  glands  require  twice  or  three 
times  as  much  blood  as  in  the  intervals. of  .their  action.  The 
force  of  the  heart,  we  have  seen,  varies  but  little  within  the 
limits  of  health,  and  the  conditions  necessary  to  the  proper 
distribution  of  blood  in  the  economy  are  regulated  almost 
exclusively  by  the  arterial  system.  These  vessels  are  not  in- 
ert tubes,  but  are  endowed  with  elasticity,  by  which  the  cir- 
culation is  considerably  facilitated,  and  with  contractility,  by 
which  the  supply  to  any  part  may  be  modified,  independent- 
ly of  the  action  of  the  heart.  Sudden  flushes  or  pallor  of  the 
countenance  are  examples  of  the  facility  with  which  this  may 
be  effected.  It  is  evident,  therefore,  that  the  properties  of 
the  coats  of  the  arteries  are  of  great  physiological  importance. 
We  will  then  commence  the  study  of  this  division  of  the  cir- 
culatory system  with  a  consideration  of  its  physiological 
anatomy. 

Physiological  Anatomy  of  the  Arteries. 

The  vessels  which  carry  the  venous  blood  to  the  lungs 
are  branches  of  a  great  trunk  which  takes  its  origin  from  the 
right  ventricle.  They  do  not  differ  in  structure  from  the 
vessels  which  carry  the  blood  to  the  general  system,  except 
in  the  fact  that  their  coats  are  somewhat  thinner  and  more  dis- 
tensible. The  aorta,  branches  and  ramifications  of  which  sup- 
ply all  parts  of  the  body,  is  given  off  from  the  left  ventricle. 
Just  at  the  origin,  behind  the  semilunar  valves,  the  aorta  has 
three  sacculated  pouches,  called  the  sinuses  of  Yalsalva.  Be- 
yond this  point  the  vessels  are  cylindrical.  As  we  recede 
16 


242  CIRCULATION. 

from  the  heart,  the  arteries  branch,  divide,  and  subdivide, 
until  they  are  reduced  to  microscopic  size.  The  branches^ 
with  the  exception  of  the  intercostal  arteries,  which  make 
nearly  a  right  angle  with  the  thoracic  aorta,  are  given  oft' 
at  an  acute  .  angle.  As  a  rule,  the  arteries  are  nearly 
straight,  taking  the  shortest  course  to  the  parts  which  they 
supply  with  blood ;  and  while  the  branches  progressively  di- 
minish in  size,  but  few  are  given  off  between  the  great  trunk 
and  the  minute  vessels  which  empty  into  the  capillary  sys- 
tem. Haller  counted  but  twenty  branches  of  the  mesenteric 
artery  between  the  aorta  and  the  capillaries  .of  the  intestines.1 
So  long  as  a  vessel  gives  off  no  branches,  its  caliber  does  not 
progressively  diminish ;  as  the  common  carotids,  which  are 
as  large  at  their  bifurcation  as  they  are  at  their  origin. 
There  are  one  or  two  instances  in  which  vessels,  though  giv- 
ing off  numerous  branches  in  their  course,  do  not  diminish 
in  size  for  some  distance ;  as  the  aorta,  which  is  as  large  at 
the  point  of  division  into  the  iliacs,  as  it  is  in  the  chest ;  and 
the  vertebral  arteries,  which  do  not  diminish  in  caliber  until 
they  enter  the  foramen  magnum.2  "With  these  exceptions,  as 
we  recede  from  the  heart,  the  caliber  of  the  vessels  progres- 
si  vely  diminishes. 

It  has  long  been  remarked  that  the  combined  caliber  of 
the  branches  of  an  arterial  trunk  is  much  greater  than  that  of 
the  main  vessel ;  so  that  the  arterial  system,  as  it  branches, 
increases  in  capacity. 

The  arrangement  of  the  arteries  is  such  that  the  requisite 
supply,  of  blood  is  sent  to  all  parts  of  the  economy  by  the 
shortest  course,  and  with  the  least  expenditure  of  force  from 
the  heart.  Generally  the  vessels  are  so  situated  as  not  to  be 
exposed  to  pressure  and  consequent  interruption  of  the  cur- 
rent of  blood ;  but  in  certain  situations,  as  about  some  of  the 
joints,  there  is  necessarily  some  liability  to  occasional  com- 

1  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  i.,  p.  220 ;  and  HALLER,  Ele- 
menta  Physiologice,  tomus  i.,  sec.  i.,  §  17. 

2  Ibid. 


PHYSIOLOGICAL   ANATOMY   OF   THE   ARTERIES.  243 

pressiori.  In  some  situations,  also,  as  in  the  vessels  going  to 
the  brain,  particularly  in  some  inferior  animals,  it  is  neces- 
sary to  moderate  the  force  of  the  blood  current,  on  account 
of  the  delicate  structure  of  the  organs  in  which  they  are  dis- 
tributed. Here  Nature  makes  a  provision  in  the  shape  of 
anastomoses ;  by  which,  on  the  one  hand,  compression  of  a 
vessel  simply  diverts,  and  does  not  arrest,  the  current  of 
blood,  and  on  the  other  hand,  the  current  is  rendered  more 
equable  and  the  force  of  the  heart  moderated. 

The  arteries  are  provided  with  membranous  sheaths,  of 
greater  or  less  strength,  as  the  vessels  are  situated  in  parts 
more  or  less  exposed  to  disturbing  influences  or  accidents. 

Researches  into  the  minute  anatomy  of  the  arteries  have 
shown  that  they  are  possessed  of  three  pretty  well  marked 
coats.  As  these  vary  very  considerably  in  arteries  of  different 
sizes,  in  their  description,  it  is  convenient  to  divide  the  ves- 
sels into  three  classes. 

1.  The  largest  arteries  •  in  which  are  included  all  that  are 
larger  than  the  carotids  and  common  iliacs. 

2.  The  arteries  of  medium  size ;    that  is,  between  the 
carotids  and  iliacs  and  the  smallest. 

3.  The  smallest  arteries  /  or  those  less  than  ^  to  -^  of  an 
inch  in  diameter.1 

The  largest  arteries  are  endowed  with  great  strength  and 
elasticity.  Their  external  coat  is  composed  of  white  or  in- 
elastic fibrous  tissue.  According  to  Kolliker,  this  coat  is  no 
thicker  in  the  largest  vessels  than  in  some  of  the  vessels  of 
medium  size.  In  some  medium-sized  vessels  it  is  actually 
thicker  than  in  the  aorta.  This  is  the  only  coat  which  is 
vascular. 

The  middle  coat,  on  which  the  thickness  of  the  vessel  de- 

1  This  is  essentially  the  division  made  by  Kolliker  (Manual  of  Human  Micro- 
scopic Anatomy,  London,  1860,  p.  485).  Some  anatomists  make  five  or  even 
more  coats  to  the  arteries.  The  three  coats  are  pretty  well  marked,  each  pos- 
sessing distinctive  properties.  The  numerous  coats  which  are  sometimes  given, 
are,  many  of  them,  simple  layers  of  the  same  tissue.  The  division  into  three  coats 
is  more  simple  and  physiological. 


244 

pends,  is  composed  chiefly  of  the  yellow  elastic  tissue.  This 
tissue  is  disposed  in  numerous  layers.  First  we  have  a  thin 
layer  of  ramifying  elastic  fibres,  and  then  a  number  of  layers 
of  elastic  membrane,  with  numerous  oval  longitudinal  open- 
ings, which  has  given  it  the  name  of  the  "  fenestrated  mem- 
brane." According  to  Kolliker,  between  the  layers  of  this 
membrane  are  found  a  few  unstriped  or  involuntary  muscu- 
lar fibres,  but  Robin  states  that  muscular  fibres  are  only  found 
in  arteries  of  medium  size.1 '  Muscular  fibres,  if  they  exist  at 
all  in  the  largest  arteries,  are  very  few,  and  of  little  physio- 
logical importance.  .  The  middle  coat  of  the  largest  arteries 
gives  them  their  yellowish  hue,  and  the  elasticity  for  which 
they  are  so  remarkable. 

The  internal  coat  of  the  largest  arteries  does  not  differ 
materially  from  the  lining  membrane  of  the  rest  of  the 
arterial  system.  It  is  identical  in  structure  with  the  endo- 
cardium, the  membrane  lining  the  cavities  of  the  heart,  and 
is  continued  through  the  entire  vascular  system.  It  is  a  thin 
homogeneous  membrane,  covered  with  a  layer  of  elongated 
epithelial  scales,  with  oval  nuclei,  their  long  diameter  fol- 
lowing the  direction  of  the  vessel. 

The  arteries  of  medium  size  possess  considerable  strength, 
some  elasticity,  and  very  great  contractility.  In  the  outer 
and  inner  coats  we  do  not  distinguish  any  great  difference 
between  them  and  the  largest  arteries,  even  in  thickness. 
The  essential  difference  in  the  anatomy  of  these  vessels  is 
found  in  the  middle  coat.  Here  we  have  a  continuation  of 
the  elastic  elements  found  in  the  largest  vessels,  but  rela- 
tively diminished  in  thickness,  and  mingled  with  the  fusiform 
involuntary  muscular  fibres,  arranged  at  right  angles  to  the 
course  of  the  vessel.  These  fibres  are  found  in  the  inner 
layers  of  the  middle  coat,  and,  according  to  Robin,  only  in 
arteries  smaller  than  the  carotids  and  primitive  iliacs.  In 
arteries  of  medium  size,  like  the  femoral,  profunda  femoris, 
radial,  or  ulnar,  they  exist  in  numerous  'layers.  There  is  no 

1  ROBIN,  in  Nysten's  Dictlonnaire  de  Medecine,  1858.     Artere. 


PHYSIOLOGICAL   ANATOMY   OF   THE   ARTERIES.  24:5 

distinct  division,  as  regards  the  middle  coat,  between  the 
largest  arteries  and  those  of  medium  size.  As  we  recede  from 
the  heart,  muscular  fibres  gradually  make  their  appearance 
between  the  elastic  layers,  progressively  increasing  in  quan- 
tity, while  the  elastic  element  is  diminished. 

In  the  smallest  arteries  the  external  coat  is  thin,  and  dis- 
appears just  before  the  vessels  empty  into  the  capillary  sys- 
tem ;  so  that  the  very,  smallest  arterioles  have  only  the  inner 
coat  and  a  layer  of  muscular  fibres. 

The  middle  coat  is  composed  of  circular  muscular  fibres, 
without  any  admixture  of  elastic  elements.  In  vessels  ^ 
of  an  inch  in  diameter,  we  have  two  or  three  layers  of  fibres; 
but  as  we  near  the  capillaries,  and  as  the  vessels  lose  the  ex- 
ternal fibrous  coat,  these  fibres  have  but  a  single  layer.1 

The  internal  coat  presents  no  difference  from  the  coat  in 
other  vessels,  with  the  exception  that  the  epithelium  is  less 
distinctly  marked,  and  is  lost  near  the  capillaries ;  the  mem- 
brane being  studded  with  longitudinal  oval  nuclei. 

A  tolerably  rich  plexus  of  vessels  is  found  in  the  external 
coats  of  the  arteries.  These  are  called  the  vasa  vasorum,  and 
come  from  the  adjacent  arterioles,  having  no  direct  connec- 
tion with  the  vessel  on  which  they  are  distributed.  A  few 
vessels  penetrate  the  external  layers  of  the  middle  coat,  but 
none  are  ever  found  in  the  internal  coat. 

Nervous  filaments,  principally  from  the  sympathetic  sys- 
tem, accompany  the  arteries,  in  all  probability,  to  their  re- 
motest ramifications :  though  they  have  not  yet  been  demon- 
strated in  the  smallest  arterioles.  These  are  not  distributed 
in  the  walls  of  the  large  vessels,  but  rather  follow  them  in 
their  course ;  their  filaments  of  distribution  being  found  in 
those  vessels  in  which  the  muscular  element  of  the  middle 
coat  predominates.  When  we  come  to  treat  of  the  physiology 
of  the  organic  system  of  nerves,  we  shall  see  that  the  "  vaso- 

1  The  structure  of  the  smallest  arteries  can  be  beautifully  exhibited  in  fresh 
microscopic  preparations  of  the  pia  mater,  in  which  the  various  points  to  which 
we  have  alluded  can  be  easily  studied. 


24:6  CIRCULATION. 

motor "  nerves  play  an  important  part    in  regulating  the 
function  of  nutrition. 

Course  of  the  Eldod  In  the  Arteries. — At  every  pulsation 
of  the  heart,  all  the  blood  contained  in  the  ventricles,  except- 
ing, perhaps,  a  few  drops,  is  forced  into  the  great  vessels. 
We  have  already  studied  the  valvular  arrangement  by  which 
the  blood,  once  forced  into  these  vessels,  is  prevented  from 
returning  into  the  ventricles  during  the  diastole.  The  sketch 
we  have  given  of  the  anatomy  of  the  arteries  has  prepared  us 
for  a  complexity  of  phenomena  in  the  circulation  in  these 
vessels,  which  would  not  obtain  if  they  were  simple,  inelastic 
tubes.  In  this  case  the  intermittent  force  of  the  heart  would 
be  felt  equally  in  all  the  vessels,  and  the  arterial  circulation 
would  be  subject  to  no  modifications  which  did  not  come 
from  the  action  of  the  central  organ.  As  it  is,  the  blood  is 
received  from  the  heart  into  vessels  endowed,  not  only  with 
great  elasticity,  but  with  contractility.  The  elasticity,  which 
is  the  prominent  property  of  the  largest  arteries,  moderates 
the  intermittency  of  the  heart's  action,  providing  a  continuous 
supply  to  the  parts ;  while  the  contractility  of  the  smallest 
arteries  is  capable  of  increasing  or  diminishing  the  supply  in 
any  part,  as  may  be  required  in  the  various  functions. 

Elasticity  of  the  Arteries. — This  property,  particularly 
marked  in  large  vessels,  has  long  been  recognized.  If,  for 
example,  we  forcibly  distend  the  aorta  with  water,  it  may  be 
dilated  to  more  than  double  its  ordinary  capacity,  and  will 
resume  its  original  size  and  form  as  soon  as  the  pressure  is 
removed.  This  simple  experiment  teaches  us,  that  if  the 
force  of  the  heart  be  sufficient  to  distend  the  great  vessels, 
their  elasticity  during  the  intervals  of  its  action  must  be 
continually  forcing  the  blood  toward  the  periphery.  The 
fact  that  the  arteries  are  distended  at  each  systole  is  abun- 
dantly proven  by  actual  experiment;  though  the  immense 
capacity  of  the  arterial  system,  compared  with  the  small 


ELASTICITY  OF   THE   ARTERIES.  247 

charge  of  blood  which  enters  at  each  pulsation,  renders  the 
actual  distention  of  the  vessels  less  than  we  should  be  led  to 
expect  from  the  force  of  the  heart's  contraction.  The  most 
satisfactory  experiments  on  this  subject  are  those  of  Poiseu- 
ille.1  This  observer  illustrated  the  dilatation  of  the  arteries 
in  the  following  way  :  Having  exposed  a  considerable  extent 
of  the  primitive  carotid  in  a  horse,  he  enclosed  a  portion  in  a 
tin  tube  filled  with  water  and  connected  with  a  small  upright 
graduated  tube  of  glass.  The  openings  around  the  artery,  as 
it  passed  in  and  out  of  the  apparatus,  being  carefully  sealed 
with  tallow,  it  is  evident  that  any  dilatation  of  the  vessel 
would  be  indicated  by  an  elevation  of  the  water  in  the  grad- 
uated tube.  This  experiment  invariably  showed  a  marked 
dilatation  of  the  artery  with  each  contraction  of  the  heart. 

"  We  remark  that  the  dilatation  is  not  very  considerable ; 
thus  it  is  not  easy  to  recognize  it  by  simple  inspection,  in  an 
artery  of  even  the  caliber  of  that  which  occupies  us,  after  we 
have  it  exposed."2 

It  being  fully  established  that  the  arteries  are  dilated  with 
each  ventricular  systole,  it  becomes  important  to  study  the 
influence  of  their  elasticity  upon  the  current  of  blood.  Divi- 
sion of  an  artery  in  a  living  animal  exhibits  one  of  the  im- 
portant phenomena  due  to  the  elastic  and  yielding  character 
of  its  walls.  We  observe,  even  in  vessels  of  considerable 
size,  as  the  carotid  or  femoral,  that  the  flow  of  blood  is  not 
intermittent,  but  remittent.  With  each  ventricular  .systole 
there  is  a  sudden  and  marked  impulse  ;  but  during  the  inter- 
vals of  contraction,  the  blood  continues  to  flow  with  consid- 
erable force.  As  we  recede  from  the  heart,  the  impulse 
becomes  less  and  less  marked ;  but  it  is  not  entirely  lost,  even 
in  the  smallest  vessels,  the  flow  becoming  constant  only  in 
the  capillary  system.  That  the  force  of  the  heart  is  abso- 
lutely intermittent,  is  shown  by  the  following  experiment : 

1  POISEUILLE,  Recherclies  sur  I1  Action  des  Artfrres  dans  la  Circulation  Arte- 
rielle. — Journal  de  Physiologic,  Paris,  1829,  tome  ix.,  p.  44. 

2  Ibid.,  p.  48. 


248  i         CIRCULATION. 

If  the  organ  be'  exposed  in  a  living  animal,  and  a  canula  be 
introduced  through  the  walls  into  one  of  the  ventricles,  we 
have  a  powerful  jet  at  each  systole,  but  no  blood  is  discharged 
during  the  diastole.  The  same  absolute  intermittency  of  the 
current  will  be  seen  if  the  aorta  be  divided.  It  is  evident 
that  we  must  look  to  the  arferies  themselves  for  the  force 
which  produces  a  flow  of  blood  in  the  intervals  of  the  heart's 
action.  The  conversion  of  the  intermittent  current  in  the 
largest  vessels  into  a  nearly  constant  flow  in  the  smallest 
arterioles  is  effected  by  the  physical  property  of  elas- 
ticity. This  may  be  illustrated  in  any  elastic  tube  of 
sufficient  length.  If  we  connect  with  a  syringe  a  series  of 
rubber  tubes  progressively  diminishing  in  caliber,  and  dis- 
charging by  a  very  small  orifice,  and  inject  water  in  an  in- 
termittent current,  if  the  apparatus  be  properly  adjusted, 
the  fluid  will  be  discharged  at  the  end  of  the  tube  in  a 
continuous  stream.  Nearer  the  syringe,  the  stream  will 
be  remittent;  and  directly  at  the  point  of  connection' of 
the  syringe  with  the  tube,  the  stream  will  be  intermittent. 
The  intermittent  impulse  may  be  said,  in  this  case,  to  be 
progressively  absorbed  by  the  elastic  walls  of  the  tube.  Each 
impulse  first  distends  that  portion  of  the  tube  nearest  to  it, 
and  further  on,  the  distention  is  diminished,  until  it  becomes 
inappreciable.  If  the  syringe  be  connected  with  two  tubes, 
one  elastic  and  the  other  inelastic,  the  current  will  be  either 
remittent  or  continuous  in  the  one,  and  intermittent  in  the 
other. 

This  modification  of  the  impulse  of  the  heart  has  great 
physiological  importance;  for  it  is  evidently  essential  that 
the  current  of  blood,  as  it  flows  into  the  delicate  capillary 
vessels,  should  not  be  alternately  intermitted,  and  impelled 
with  the  full  power  of  the  ventricle.  After  all,  it  is  in  the 
capillaries  that  the  blood  performs  its  functions,  and  here  we 
should  have  a  constant  supply  of  the  fluid  in  proper  quantity 
and  in  proper  condition  to  meet  the  nutritive  requirements 
of  the  parts. 


ELASTICITY   OF   THE  ARTERIES.  249 

The  elasticity  of  the  arteries  favors  the  flow  of  the  blood 
toward  the  capillaries  by  a  mechanism  which  is  easily  un- 
derstood. The  blood  discharged  from  the  heart  distends  the 
elastic  vessel,  which  reacts,  after  the  distending  force  ceases 
to  operate,  and  compresses  its  fluid  contents.  This  reaction 
would  have  a  tendency  to  force  the  blood  in  two  directions, 
were  it  not  for  an  instantaneous  closure  of  the  valves,  which 
makes  regurgitation  impossible.  The  influence  then  can  only 
be  exerted  in  the  direction  of  the  periphery  ;  and,  if  we  can 
imagine  as  divided  an  action  which  is  propagated  with  such 
rapidity,  the  reaction  of  that  portion  of  the  vessel  immedi- 
ately distended  by  the  heart,  distends  a  portion  farther  on, 
which  in  its  turn  distends  another  portion,  and  so  the  wave 
passes  along  until  the  blood  is  discharged  into  the  capillaries. 
In  this  way  we  can  see  that  in  vessels  removed  a  sufficient 
distance  from  the  heart,  the  force  exerted  on  the  blood  by 
the  reaction  of  the  elastic  walls  is  competent  to  produce  a 
very  considerable  current  during  the  intervals  of  the  heart's 
contraction. 

This  theoretical  view  is  fully  carried  out  by  the  following 
simple  and  conclusive  experiment  of  M.  Marey.  He  con- 
nected two  tubes  of  equal  size,  one  of  rubber  and  the  other 
of  glass,  with  the  stop-cock  of  a  large  vase  filled  with  water. 
The  elastic  tube  was  provided  with  a  valve  near  the  stop- 
cock, which  prevented  the  reflux  of  fluid,  and  both  were 
fitted  with  tips  of  equal  caliber.  When,  by  alternately  opening 
and  closing  the  stop-cock,  water  was  allowed  to  flow  into  these 
tubes  in  an  intermittent  stream,  it  was  found  that  a  greater 
quantity  was  discharged  by  the  elastic  tube ;  but  an  equal 
quantity  was  discharged  by  both  tubes  when  the  stop-cock 
was  left  open,  and  the  fluid  allowed  to  pass  in  a  continuous 
stream.1 

This  simple  experiment  shows  that  not  only  does  the  elas- 
ticity of  the  arteries  convert  the  intermittent  current  in  the 
largest  vessels  into  a  current  more  and  more  nearly  contin- 

1  MAREY,  Circulation  du  Sang^  Paris,  1863,  pp.  128,  131. 


250  CIRCULATION. 

nous  as  we  approach  the  periphery,  but  that  when  reflux  is 
prevented,  as  it  is  by  the  semilunar  valves,  the  resiliency  of 
the  arteries  assists  the  circulation. 

Contractility  of  the  Arteries. — It  is  a  fully  established 
anatomical  fact  that  the  medium-sized  and  smallest  arteries 
contain  contractile  or  muscular  elements ;  and  it  is  also  a 
fact,  proven  by  actual  experiment,  that  as  a  consequence  of 
the  condition  of  these  fibres,  the  vessels  undergo  considerable 
variation  in  their  caliber.  The  opinions  of  the  older  physi- 
ologists on  this  question  have  only  an  historical  interest,  and 
will  not,  therefore,  be  discussed.  Among  the  more  recent 
investigations  on  this  subject,  we  have  the  experiments  of  Cl. 
Bernard  and  Schiif,  which  have  been  repeatedly  confirmed, 
showing  that  through  the  nervous  system  the  muscular  coats 
of  arteries  may  be  readily  made  to  contract  or  become  re- 
laxed. If  the  sympathetic  be  divided  in  the  neck  of  a  rab- 
bit, in  a  very  few  minutes  the  arteries  of  the  ear  on  that  side 
are  notably  dilated.  If  the  divided  extremity  of  the  nerve 
be  feebly  galvanized,  the  vessels  soon  take  on  contraction,  and 
may  become  smaller  than  on  the  opposite  side.  These  expe- 
riments demonstrate,  in  the  most  conclusive  manner,  the  con- 
tractile properties  of  the  small  arteries,  and  give  us  an  idea 
how  the  supply  of  blood  to  any  particular  part  may  be  regu- 
lated. The  vessels  may  be  most  effectually  excited  through 
the  nervous  system  ;  and  it  is  on  account  of  the  difficulty  in 
producing  marked  results  by  direct  irritation,  that  the  older 
physiologists  were  divided  on  the  subject  of  their  "  irrita- 
bility." 

The  contractility  of  the  arteries  has  great  physiological 
importance.  As  their  function  is  simply  to  supply  blood  to 
the  various  tissues  and  organs,  it  is  evident  that  wrhen  the 
vessels  going  to  any  particular  part  are  dilated,  the  supply 
of  blood  is  necessarily  increased.  This  is  particularly  impor 
tant  in  the  glands,  which,  during  the  intervals  of  secretion, 
receive  a  comparatively  small  quantity  of  blood.  Bernard 


CONTEACTILITY  OF  THE  AETEEIES.  251 

has  shown,  by  a  beautiful  series  of  experiments,  which  will 
be  more  particularly  alluded  to  on  the  subject  of  secretion, 
that  galvanization  of  what  he  calls  the  motor  nerve  of  a 
gland  dilates  the  vessels,  largely  increases  the  supply*  of  blood, 
and  induces  secretion  ;  while  galvanization  of  the  sympathetic 
filaments  contracts  the  vessels,  diminishes  the  supply  of  blood, 
and  arrests  secretion.  The  pallor  of  parts  exposed  to  cold, 
and  the  flush  produced  by  heat,  are  due,  on  the  one  hand,  to 
contraction,  and  on  the  other  to  dilatation  of  the  small  arter- 
ies. Pallor  and  blushing  from  mental  emotions  are  examples 
of  the  same  kind  of  action. 

The  ulterior  eifects  on  nutrition,  which  result  from  dila- 
tation of  the  vessels  of  a  part,  are  of  great  interest.  When  the 
supply  of  blood  is  much  increased,  as  in  section  of  the 
sympathetic  in  the  neck,  nutrition  is  exaggerated,  and  the 
temperature  is  raised  beyond  that  of  the  rest  of  the  body. 

The  idea,  which  at  one  time  obtained,  that  the  arteries 
were  the  seat  of  rhythmical  contractions,  which  had  a  favor- 
able influence  on  the  current  of  blood,  is  entirely  erroneous.1 
It  is  hardly  necessary  to  repeat  that  the  prime  cause  of 
the  arterial  circulation  is  the  force  of  the  ventricles.  We 
have  seen  that  the  elasticity  of  the  arteries  produces  a  flow 
during  the  intervals  of  the  heart's  action,  and  the  question 
now  arises  whether  the  force  thus  exerted  is  simply  a  re- 
turn of  the  force  required  to  expand  the  vessels,  which  has 
been  borrowed,  as  it  were,  from  the  heart,  or  is  something 
superadded  to  the  force  of  the  heart.  The  experiment  of 
Marey,  already  alluded  to,  settles  this  question.  "When 
water  was  forced  in  an  intermittent  current  into  two  tubes, 
one  elastic  and  the  other  inelastic,  but  discharging  by  open- 
ings of  equal  size,  by  far  the  greater  quantity  was  discharged 
by  the  elastic  tube.  A  little  reflection  will  show  how  the 

1  Schiff  has  noticed  rhythmical  contractions  in  the  superficial  arteries  of  the 
ear  in  the  rabbit,  and  some  other  animals;  but  this  phenomenon  is  excep- 
tional, and  the  movements  do  not  appear  to  favor  the  current  of  blood. 
(MILNE-EDWARDS,  Physiologic  tome,  iv.,  p.  217.) 


252  CTECULATIOK". 

action  of  the  elastic  arteries  must  actually  assist  the  circula- 
tion. The  resiliency  of  the  vessels  is  continually  pressing  their 
contents  toward  the  periphery,  as  regurgitation  is  rendered 
impossible  by  the  action  of  the  semilunar  valves.  The  dila- 
tation of  the  vessels  with  each  systole,  of  course,  admits  an 
increased  quantity  of  blood ;  *and  it  has  been  experimentally 
demonstrated,  that  the  same  intermittent  force  exerted  on 
an  inelastic  tube,  will  discharge  a  less  quantity  of  liquid 
from  openings  of  equal  caliber. 

Superadded,  then,  to  the  force  of  the  heart,  we  must 
recognize,  as  a  cause  influencing  the  flow  of  blood  in  the 
arteries,  the  resiliency  of  the  vessels,  especially  those  of  large 
size. 

Thus  it  will  be  seen  that  the  arteries  are  constantly  kept 
distended  with  blood  by  the  heart,  and  by  virtue  of  their 
elasticity  and  the  progressive  increase  in  the  capacity  of  this 
system  as  they  branch,  the  powerful  contractions  of  the  cen- 
tral organ  only  serve  to  keep  up  an  equable  current  in  the 
capillaries.  The  small  vessels,  by  virtue  of  their  contractile 
walls,  regulate  the  distribution  of  the  blood ;  acting  as  the 
guards  or  sentinels  of  the  process  of  nutrition,  and,  in  fact, 
all  the  numerous  functions  in  which  the  blood  is  concerned. 
Obeying  the  commands  transmitted  through  the  sympathetic 
nervous  system,  they  allow  the  passage  to  every  part  of  the 
proper  quantity  of  the  nutritive  fluid  at  the  proper  time. 

Locomotion  of  the  Arteries  and  Production  of  the  Pulse. — 
At  each  contraction  of  the  heart,  the  arteries  are  increased  in 
length,  and  many  of  them  undergo  a  considerable  locomo- 
tion. This  may  be  readily  observed  in  vessels  which  are 
tortuous  in  their  course,  and  is  frequently  very  marked  in  the 
temporal  artery  in  old  persons.  The  elongation  may  also  be 
seen  if  we  watch  attentively  the  point  where  an  artery  bifur- 
cates, as  at  the  division  of  the  common  carotid.  It  is  simply 
the  mechanical  effect  of  sudden  distention ;  which,  while  it 


PRODUCTION  OF  THE  PULSE.  253 

increases   the   caliber  of  the  vessel,  causes    an    elongation 
even  more  marked. 

TKe  linger  placed  over  an  exposed  artery,  or  one  which 
lies  near  the  surface,  experiences  a  sensation  at  every  beat 
of  the  heart,  as  though  the  vessel  were  striking  against  it. 
This  has  long  been  observed,  and  is  called  the  pulse.  Ordi- 
narily it  is  appreciated  when  the  current  of  blood  can  be 
subjected  to  a  certain  amount  of  obstruction,  as  in  the  radial, 
which  can  readily  be  compressed  against  the  bone.  In  an 
artery  imbedded  in  soft  parts,  which  yield  to  pressure,  the 
actual  dilatation  of  the  vessel  being  very  slight,  pulsation  is 
felt  with  difficulty,  if  at  all.  When  obstruction  is  complete, 
as  in  ligation  of  a  vessel,  the  pulsation  above  the  point  of 
ligature  is  very  marked,  and  can  be  readily  appreciated  by 
the  eye.  The  explanation  of  this  exaggeration  of  the  move- 
ment is  the  following :  JSTormally,  the  blood  passes  freely 
through  the  arteries,  and  produces,  in  the  smaller  vessels, 
very  little  movement  or  dilatation  ;  but  when  the  current  is 
obstructed,  as_by  ligation,  or  even  compression  with  the 
finger,  the  force  of  the  heart  is  not  sent  through  the  vessel  to 
the  periphery,  but  is  arrested,  and  therefore  becomes  more 
marked  and  easily  appreciated.  In  vessels  which  have  be- 
come undilatable  and  incompressible  from  calcareous  deposit, 
the  pulse  cannot  be  felt.  The  character  of  the  pulse  in- 
dicates,, to  a  certain  extent,  the  condition  of  the  heart  and 
vessels.  We  have  spoken,  when  treating  of  the  heart,  of 
the  varying  rapidity  of  the  pulse,  as  it  is  a  record  of  the 
rapidity  of  the  action  of  this  organ ;  but  it  remains  for  us 
to  consider  the  mechanism  of  its  production,  and  its  various 
characters. 

Under  ordinary  circumstances,  the  pulse  may  be  felt  in 
all  arteries  which  are  exposed  to  investigation ;  and  as  it  is 
due  to  the  movement  of  the  blood  in  the  vessels,  the  prime 
cause  of  its  production  is  the  contraction  of  the  left  ventriqle. 
The  late  very  interesting  experiments  of  M.  Marey  have 
shown  that  the  impulse  given  to  the  blood  by  the  heart  is 


254  CIRCULATION. 

not  felt  in  all  the  vessels  at  the  same  instant.  By  ingenious 
contrivances,  which  will  be  described  further  on,  this  observer 
has  succeeded  in  registering  simultaneously  the  impulse  of 
the  heart,  the  pulse  of  the  aorta,  and  the  pulse  of  the  femoral 
artery.  He  has  thus  ascertained  that  the  contraction  of  the 
ventricle  is  anterior  to  the  pulsation  of  the  aorta,  and  the 
pulsation  of  the  aorta  precedes  the  pulse  in  the  femoral.1 
This  only  confirms  the  views  of  other  physiologists,  particu- 
larly Weber,  who  described  this  progressive  retardation  of 
the  pulse  as  we  recede  from  the  heart,  estimating  the  differ- 
ence between  the  ventricular  systole  and  the  pulsation  of  the 
artery  in  the  foot,  at  one-seventh  of  a  second.8  The  observa- 
tions of  M.  Marey  are  particularly  referred  to  as  being  the 
most  conclusive. 

It  is  evident  from  what  we  know  of  the  variations  which 
occur  in  the  force  of  the  heart's  action,  the  quantity  of  blood 
in  the  vessels,  and  from  the  changes  which  may  take  place  in 
the  caliber  of  the  arteries,  that  the  character  of  the  pulse 
must  be  subject  to  numerous  variations.  Many  of  these  may 
be  appreciated  simply  by  the  sense  of  touch.  We  find  wri- 
ters treating  of  the  soft  and  compressible  pulse,  the  hard 
pulse,  the  wiry  pulse,  the  thready  pulse,  etc.,  as  indicating 
various  conditions  of  the  circulatory  system.  The  character 
of  the  pulse,  aside  from  its  frequency,  has  always  been  re- 
garded as  of  great  importance  in  disease ;  and  the  variations 
w7hich  occur  in  health  form  a  most  interesting  subject  for 
physiological  inquiry. 

Form  of  the  Pulse. — It  is  evident  that  few  of  the  charac- 
ters of  a  pulsation,  occupying  as  it  does  but  a  seventieth 
part  of  a  minute,  can  be  ascertained  by  the  sense  of  touch 

1  MAREY,  Circulation  du  Sang,  p.  197.  In  an  article  published  in  the 
Journal  de  la  Physiologic,  1859,  tome  ii.,  p.  267,  Marey  took  ground  against 
the" progressive  retardation  of  the  pulse  in  arteries  removed  from  the  heart ;  but 
in  his  last  work  the  fact  is  admitted,  and  seems  proven  beyond  a  doubt. 

a  MILNE-EDWARDS,  Physiologic,  tome  iv.,  p.  188. 


FORM   OF  THE   PULSE.  255 

alone.  This  fact  lias  been  appreciated  by  physiologists ;  and 
within  the  last  few  years,  in  order  to  accurately  study-this 
important  subject,  instruments  for  registering  the  impulse 
felt  by  the  arterial  system  have  been  constructed,  to  enable 
us  to  accurately  analyze  the  dilatation  or  movements  of  the 
vessels.  The  idea  of  such  an  instrument  was  probably  sug- 
gested by  the  following  simple  observation  :  When  the  legs 
are  crossed,  with  one  knee  over  the  other,  the  beating  of  the 
popliteal  artery  will  produce  a  marked  movement  in  the  foot. 
If  we  could  apply  to  an  artery  a  lever  provided  with  a  mark- 
ing point  in  contact  with  a  slip  of  paper  moving  at  a  definite 
rate,  this  point  would  register  the  movements  of  the  vessel, 
and  its  changes  in  caliber.  The  first  physiologist  who  put 
this  in  practice  was  Yierordt,  who  constructed  quite  a  com- 
plex instrument,  so  arranged  that  the  impulse  from  an  acces- 
sible artery,  like  the  radial,  was  conveyed  to  a  lever,  which 
marked  the  movement  upon  a  revolving  cylinder  of  paper. 
This  instrument  was  called  a  "  sphygmograph."  The  traces 
made  by  it  were  perfectly  regular,  and  simply  marked  the 
extremes  of  dilatation,  exaggerated,  of  course,  by  the  length 
of  the  lever,  and  the  number  of  pulsations  in  a  given  time. 
The  latter  can,  of  course,  be  easily  estimated  by  more  simple 
means ;  and  as  the  former  did*  not  convey  any  very  definite 
physiological  idea,  the  apparatus  was  regarded  rather  as  a 
curiosity  than  an  instrument  for  accurate  research. 

The  principle  on  which  the  instrument  of  Vierordt  was 
constructed  was  correct,  and  it  only  remained  to  construct 
one  which  would  be  easy,  of  application,  and  produce  a 
trace  representing  the  shades  of  dilatation  and  contraction 
of  the  vessels,  in  order  to  lead  to  important  practical  results. . 
These  indispensable  conditions  are  fully  realized  in  the 
sphygmogragh  of  M.  Marey,  to  whose  researches  on  the  cir- 
culation we  have  repeatedly  referred.  The  instrument  sim- 
ply amplifies  the  changes  in  the  caliber  of  the  vessel,  without 
deforming  them  ;  and  though  its  application  is,  perhaps,  not  so 
easy  as  to  make  it  generally  useful  in  practice,  in  the  hands 


256 


CIRCULATION. 


of  Marey  it  has  given  us  a  definite  knowledge  of  the  physio- 
logical character  of  the  pulse,  and  its  modifications  in  certain 


FIG.  3. 


Sphygmograph  of  Marey.  The  apparatus  is  securely  fixed  on  the  forearm,  so  that  the 
spring  under  the  screw  V  is  directly  over  the  radial  artery.  The  movements  of  the 
pulse  are  transmitted  to  the  long  and  light  wooden  lever  L,  and  registered  upon  the 
surface  P,  which  is  moved  at  a  known  rate  by  the  clock-work  H.  The  apparatus  is  so 
adjusted  that  the  movements  of  the  vessel  are  accurately  amplified  and  registered  by 
the  extreme  point  of  the  lever.  (MABEY,  Recherches,  etc.— Journal  de  la  jihysiologie, 
Paris,  1860,  tome  iii.,  p.  244.) 

diseases ;  information  which  is  exceedingly  desirable,  and 
could  not  be  arrived  at  by  other  means  of  investigation.  In 
short,  its  mechanism  is  so  accurate  that,  when  skilfully  used, 
it  gives  on  paper  the  actual  "form  of  the  pulse? 


FIG.  4. 


Trace  of  Vierordt  (Ibid.). 


This  instrument,  applied  to  the  radial  artery,  gives  a 
trace  very  different  from  that  obtained  by  Yierordt,  which 


FORM   OF   THE   PULSE.  257 

was  simply  a  series  of  regular  elevations  and  depressions. 
A  comparison  of  the  traces  obtained  by  these  two  observers 
gives  an  idea  of  the  defects  which  have  been  remedied  by 
Marey  ;  for  it  is  'evident  that  the  dilatation  and  contraction  of 

TIG.  5. 


Trace  of  Marey.    Portions  of  four  traces  taken  in  different  conditions  of  the  pulse  (Ibid.) 

the  arteries  cannot  be  as  regular  and  simple  as  would  be  in- 
ferred merely  from  the  trace  made  by  the  instrument  of 
Yierordt. 

Analyzing  the  traces  of  Marey,  we  see  that  there  is  a 
dilatation  following  the  systole  of  the  heart,  marked  by  an 
elevation  of  the  lever,  more  or  less  sudden,  as  indicated  by 
the  angle  of  the  trace,  and  of  greater  or  less  amplitude.  The 
dilatation,  having  arrived  at  its  maximum,  is  followed  by 
contraction ;  which  may  be  slow  and  regular,  or  may  be,  and 
generally  is,  interrupted  by  a  second  and  slighter  upward 
movement  of  the  lever.  This  second  impulse  varies  very 
much  in  amplitude.  In  some  rare  instances  it  is  nearly  as 
marked  as  the  first,  and  may  be  appreciated  by  the  finger, 
giving  the  sensation  of  a  double  pulse  following  each  con- 
traction of  the  heart.  This  is  called  the  dicrotic  pulse. 

As  a  rule,  the  first  dilatation  of  the  vessel  is  sudden,  and 
indicated  by  an  almost  vertical  line ;  this  is  followed  by  a 
slow  reaction,  indicated  by  a  gradual  descent  of  the  trace, 
which  is  not,  however,  absolutely  regular,  but  marked  by  a 
slight  elevation  indicating  a  second  impulse. 

The  amplitude  of  the  trace,  or  the  distance  between  the 
highest  and  lowest  points  marked  by  the  lever,  depends  upon 
the  amount  of  constant  tension  of  the  vessels.  Marey  has 
found  that  the  amplitude  is  in  an  inverse  ratio  to  the  tension ; 
which  is  very  easily  understood,  for  when  the  arteries  are  little 
distended,  the  force  of  the  heart  must  be  more  marked  in  its 
17 


258  CIRCULATION. 

effects  than  when  the  pressure  of  blood  in  them  is  very  great. 
Any  circumstance  which  facilitates  the  flow  of  blood  from 
the  arteries  into  the  capillaries,  will,  of  course,  relieve  the 
tension  of  the  arterial  system,  lessen  the  obstacle  to  the  force 
of  the  heart,  and  increase  the  amplitude  of  the  pulsation ; 
and  vice  versa.  In  support  of  this  view,  Marey  has  found 
that  cold  applied  to  the  surface  of  the  body,  contracting,  as 
it  does,  the  smallest  arteries,  increases  the  arterial  tension 
and  diminishes  the  amplitude  of  the  pulsation ;  while  a  mod- 
erate elevation  of  temperature  produces  an  opposite  effect. 

In  nearly  all  the  traces  given  by  Marey ,.  the  descent  of 
the  lever  indicates  more  or  less  oscillation  of  the  mass  of  blood. 
The  physical  properties  of  the  larger  arteries  render  this 
inevitable.  As  they  yield  to  the  distending  influence  of  the 
heart,  reaction  occurs  after  this  force  is  taken  off,  and,  if  the 
distention  be  very  great,  gives  a  second  impulse  to  the  blood. 
This  is  quite  marked,  unless  the  tension  of  the  arterial  system 
be  so  great  as  to  offer  too  much  resistence.  One  of  the  most 
favorable  conditions  for  the  manifestation  of  dicrotism  is 
diminished  tension,  which  is  always  found  coexisting  with  a 
very  marked  exhibition  of  this  phenomenon. 

The  delicate  instrument  employed  by  Marey  enabled  him 
to  accurately  determine  and  register  these  various  phenomena, 
by  observations  on  arteries  of  the  human  subject  and  animals ; 
and  by  means  of  an  ingeniously  constructed  " schema"  rep- 
resenting the  arterial  system  by  elastic  tubes,  and  the  left  ven- 
tricle by  an  elastic  bag,  provided  with  valves,  acting  as  a  syr- 
inge, he  satisfactorily  established  the  conditions  of  tension, 
etc.,  necessary  to  their  production.  In  this  schema,  the  regis- 
tering apparatus,  simpler  in  construction  than  the  sphygmo- 
graph,  could  be  applied  to  the  tubes  with  more  accuracy 
and  ease. 

He  demonstrated,  by  experiments  with  this  system  of 
tubes,  that  the  amplitude  of  the  pulsations,  the  force  of  the 
central  organ  being  the  same,  is  greatest  when  the  tubes  are 
moderately  distended,  or  the  tension  of  fluid  is  low,  and  vice 


FOKM   OF   THE   PULSE.  259 

versa.  He  demonstrated,  also,  that  a  low  tension  favors 
dicrotism.  In  this  latter  observation  he  diminished  the  ten- 
sion by  enlarging  the  orifices  by  which  the  fluid  is  discharged 
from  the  tubes,  imitating  the  dilatation  of  the  small  vessels, 
by  which  the  tension  is  diminished  in  the  arterial  system. 
He  also  demonstrated  that  an  important  and  essential  element 
in  the  production  of  dicrotism,  is  the  tendency  to  oscillation 
of  the  fluid  in  the  vessels,  between  the  contractions  of  the 
heart.  This  can  only  occur  in  fluid  which  has  a  certain 
weight,  and  acquires  a  velocity  from  the  impulse;  for 
when  air  was  introduced  into  the  apparatus,  dicrotism  could 
not  be  produced  under  any  circumstances,  as  the  fluid  did 
not  possess  weight  enough  to  oscillate  between  the  impulses. 
Water  produced  a  well-marked  dicrotic  impulse  under  favor- 
able circumstances;  and  with  mercury,  the  oscillations  made 
two,  three,  or  more  distinct  impulses. 

By  these  experiments  he  proved  that  the  blood  oscillates 
in  the  vessels,  if  this  movement  be  not  suppressed  by  too  great 
pressure,  or  tension.  This  oscillation  gives  the  successive 
rebounds  that  are  marked  in  the  descending  line  of  the 
pulse,  and  is  capable,  in  some  rare  instances,  when  the  arte- 
rial tension  is  very  slight,  of  producing  a  second  rebound  of 
sufficient  force  to  be  appreciated  by  the  finger.1 

1  In  treating  of  the  form  of  the  pulse,  of  course  including  dicrotism,  from  a 
purely  physiological  point  of  view,  we  have  given  an  analysis  of  the  physiological 
portion  of  the  late  work  of  MAREY  (Physiologic  Medicate  de  la  Circulation  du 
Sang,  Paris,  1863).  To  portions  of  this  work  relating  to  the  action  of  the  heart, 
sounds,  etc.,  we  have  already  referred.  As  is  evident  from  our  sketch  of  the 
instruments  for  registering  the  pulse,  the  author  referred  to  is  the  only  one  who 
has  produced  a  trace  correctly  representing  the  shades  of  locomotion  and  dilatation 
of  the  arteries ;  and  by  his  brilliant  and  ingenious  experiments,  which  cannot  be 
too  highly  praised,  he  has  settled  many  important  points,  and  given  a  precious 
means  of  investigation  to  other  physiologists.  He  has  opened  a  new  field  for 
study  of  the  pathological  changes  in  the  form  of  the  pulse;  but  before  we 
can  advance  far  in  this  direction,  we  must  become  familiar  with  all  the  modi- 
fications which  occur  in  health,  an  end  which  as  yet  is  by  no  means  fully  attained. 
The  construction  of  a  sphygmograph  was  a  problem  of  great  delicacy,  and  a 
certain  amount  of  practical  experience  with  the  instrument  has  convinced  us  of 


260  CIRCULATION. 

"Without  treating  of  the  variations  in  the  character  of  the 
pulse  in  disease,  due  to  the  action  of  the  muscular  coat,  we 
•will  consider  some  of  the  external  modifying  influences  which 
come  within  the  range  of  physiology.  The  smallest  vessels 
and  those  of  medium  size  possess  to  an  eminent  degree  what 
is  called  tonicity,  or  the  property  of  maintaining  a  certain 
continued  amount  of  contraction.  This  contraction  is  antag- 
onistic to  the  distending  force  of  the  blood,  as  is  shown  by 
opening  a  portion  of  an  artery  included  between  two  ligatures, 
in  a  living  animal,  when  the  contents  will  be  forcibly  dis- 
charged and  the  caliber  of  that  portion  of  the  vessel  very 
much  diminished.  Too  great  distention  of  the  vessels  by 
the  pressure  of  blood  seems  to  be  prevented  by  this  constant 
action  of  the  muscular  coat;  and  thus  the  conditions  are 
maintained  which  give  the  pulse  the  character  we  have  just 
described. 

By  excessive  and  continued  heat,  the  muscular  tissue  of  the 
arteries  may  be  dilated  so  as  to  offer  less  resistance  to  the 
distending  force  of  the  heart.  Under  these  circumstances, 
the  pulse,  as  felt  by  the  finger,  will  be  found  to  be  larger  and 
softer  than  normal.  Cold,  either  general  or  local,  has  a  pre- 
cisely opposite  effect ;  the  arteries  become  contracted,  and 
the  pulse  assumes  a  harder  and  more  wiry  character.  Usually, 
prolonged  contraction  of  the  arteries  is  followed  by  relaxation, 
as  is  seen  in  the  full  pulse  and  glow  of  the  surface  which 
accompany  reaction  after  exposure  to  cold. 

It  has  been  found,  also,  that  there  is  a  considerable  differ- 

the  accuracy  of  results  to  be  obtained  when  it  is  used  with  skill  and  care ;  but  the 
very  perfection  and  nicety  of  the  instrument  present  almost  insurmountable 
difficulties  in  the  way  of  its  use  by  the  general  practitioner.  Results,  regarding 
the  amplitude  of  pulsations  especially,  should  be  received  with  great  caution,  from 
the  extreme  difficulty  of  adjusting  the  lever  so  as  to  give  the  maximum  of  the 
impulse.  It  does  not  appear,  however,  how  these  drawbacks  to  the  general  use 
of  the  instrument  can  be  obviated;  for  its  construction  leaves  nothing  to  be 
desired,  and  the  delicacy  of  its  adjustment,  like  that  of  a  fine  balance,  is  indis- 
pensable. In  the  hands  of  Marey,  its  results,  we  conceive,  are  to  be  fully  ao 
cepted. 


AKTEKIAL   PRESSURE.  261 

ence  in  the  caliber  of  the  arteries  at  different  periods  of  the 
day.  The  diameter  of  the  radial  has  been  found  very  much 
greater  in  the  evening  than  in  the  morning,1  producing, 
naturally,  a  variation  in  the  character  of  the  pulse.  "We 
learn  from  these  physiological  variations,  how  in  disease, 
when  they  become  more  considerable,  they  may  give 
important  information  with  regard  to  the  condition  of  the 
system. 

Pressure  of  Blood  in  the  Arteries. 

The  reaction  of  the  elastic  walls  of  the  arteries  during  the 
intervals  of  the  heart's  action  gives  rise  to  a  certain  amount 
of  constant  pressure,  by  which  the  blood  is  continually  forced 
toward  the  capillaries.  The  discharge  of  blood  into  the  ca- 
pillaries has  a  constant  tendency  to  diminish  this  pressure ; 
but  the  contractions  of  the  left  ventricle,  by  forcing  repeated 
charges  of  blood  into  the  arteries,  have  a  compensating  ac- 
tion. By  the  equilibrium  between  these  two  agencies,  a 
certain  degree  of  tension  is  maintained  in  the  arteries,  which 
is  called  the  arterial  pressure. 

The  first  experiments  with  regard  to  the  extent  of  the 
arterial  pressure  were  made  by  Hales  an  English  physiolo- 
gist, more  than  a  hundred  years  ago.2  This  observer,  adapt- 
ing a  long  glass  tube  to  the  artery  of  a  living  animal,  ascer- 
tained the  height  of  the  column  of  blood  which  could  be 
sustained  by  the  arterial  pressure.  In  some  experiments  on 
the  carotid  of  the  horse,  the  blood  mounted  to  the  height  of 
from  eight  to  ten  feet.  Hales  was  not  fully  acquainted  with 
the  influences  capable  of  modifying  the  arterial  pressure,  and 
his  estimates  of  the  normal  tension  in  these  vessels  were  not 
entirely  correct.  It  is  now  ascertained  that  the  pressure  in 
the  arteries  will  sustain  a  column  of  about  six  feet  of  water, 
or  six  inches  of  mercury,  and  is  subject  to  considerable  vari- 

1  MILNE-EDWARDS,  op.  tit.,  tome  iv.,  p.  222. 

2  HALES,  Statical  Essays,  London,  1733,  vol.  ii.,  HcemastaticJcs. 


262 


CIRCULATION". 


Fi?.  6. 


ations,  depending  upon  the  condition  of  the  heart  and  ves- 
sels, the  quantity  of  blood,  respiration,  muscular  exercise,  etc. 
All  experiments  on  the  arterial  pressure  are  made  on  the 
principle  of  the  experiment  of  Hales,  which,  with  reference 
simply  to  the  constant  pressure  in  the  arteries,  is  as  useful  as 
those  of  later  date,  and  mue*h  more  striking.  The  only  in- 
convenience is  in  the  manipulation  of  the  long  tube,  but  this 
may  be  avoided  by  setting  it  in  a  strip  of  wood,  when  it  can 
be  easily  handled.  If  a  large  artery,  as  the  carotid,  be  ex- 
posed in  a  living  animal,  and 
a  metallic  point,  connected  with 
a  vertical  tube  of  small  caliber 
and  from  seven  to  eight  feet 
long  by  a  bit  of  elastic  tubing, 
be  secured  in  the  vessel,  the 
blood  will  rise  to  the  height  of 
about  six  feet,  and  remain  at 
this  point  almost  stationary, 
indicating  by  a  slight  pulsatile 
.movement  the  action  of  the 
heart.  On  carefully  watching 
the  level  in  the  tube,  in  addi- 
tion to  the  rapid  oscillation  co- 
incident with  the  pulse,  another 
oscillation  will  be  observed, 
which  is  less  frequent,  and 
which  corresponds  with  the 
movements  of  respiration.  The 
pressure,  as  indicated  by  an 

llaemodynamometer  of  Poiseuille,  modified     elevation  of  the  fluid,  IS  sliffllt- 
by  Ludwig,  Spongier,  and  Valentin.     The  IT.' 

1    ly    increased    during    expira- 
and  diminished 


tion, 


during 


instrument  is  connected  with  the  vessel 
V  V,  in  such  a  manner  that  the  circula- 
tion is  not  interrupted.  The  elevation  of 
the  mercury  in  the  branch  B  C  indicates 
the  amount  of  pressure.  (BECLAKD,  Phy-  inspiration 
tiologie,  Paris,  1859,  p.  204.) 

1  In  all  these  experiments  on  the  arterial  or  cardiac  pressure,  it  is  necessary 
to  fill  part  of  the  tube,  or  whatever  apparatus  we  may  use,  with  a  solution  of  car- 
bonate of  soda,  in  order  to  prevent  coagulation  of  the  blood  as  it  passes  out  of 
the  vessels. 


AKTEEIAL  PEESSUEE. 


263 


The  experiment  with  the  long  tube  gives  us  the  best  idea 
of  the  arterial  pressure,  which  will  be  found  to  vary  from  five 
and  a  half  to  six  feet  of  blood,  Fis- 7- 

or  a  few  inches  more  of  water. 
The  oscillations  produced  by 
the  contractions  of  the  heart  are 
not  very  marked,  on  account  of 
the  immense  friction  in  so  long 
a  tube  ;  but  this  is  favorable  to 
the  study  of  the  constant  press- 
ure in  the  arteries.  It  has  been 
found  that  the  estimates  above 
given  do  not  vary  very  much 
in  animals  of  different  sizes. 
Bernard  found  the  pressure  in 
the  carotid  of  a  horse  little 
more  than  in  the  dog  or  rab- 
bit. In  the  larger  animals  it 
is  the  force  of  the  heart  which 
is  increased,  and  not  to  any 
considerable  extent  the  con- 
stant pressure  in  the  vessels.1  ' 

The  experiments  of  Hales 
were  made  with  a  view  of  cal- 

Section  of  the  cardiometer  of  Magendie,  as 
modified  by  Bernard.  A  strong  glass  bottle 
is  perforated  at  each  side,  and  fitted  with  an 
iron  tube,  with  an  opening,  T,  by  which  the 
mercury  enters.  One  end  of  the  iron  tube 
is  closed,  and  the  other  is  bent  upwards  and 
connected  with  the  graduated  glass  tube  T', 
Avhich  has  a  caliber  of  from  f  5  to  £  of  an  inch. 
The  bottle  is  filled  with  mercnry  until  it 
rises  to  n'  in  the  tube  which  is  marked  O. 
The  cork  is  perforated  by  the  tube  £,  which 


and  were  not  directed  particu- 
larly to  the  conditions  and  va- 
riations of  the  arterial  pressure. 
It  is  only  since  the  experiments 
performed  by  Poiseuille  with 
the  iKKinodynamometer^  in  1828, 
that  we  have  any  reliable  data 
on  this  latter  point.8  Poiseuille's  instrument  for  measuring 
the  force  of  the  blood  is  a  simple  graduated  U  tube,  half 


is  connected  by  a  rubber  tube  with  the  point 
C,  which  is  introduced  into  the  vessel. 
(BERNARD,  Liquides  de  POrganisme,  Paris, 
1859,  tome  i.,  p.  167.) 


1  BERNARD,  lAquides  de  V 'Organismc,  Paris,  1859,  tome  i.,  p.  172. 

a  POISEUILLE,  Recherche*  sur  la  Force  du  Cceur  Aortique,  Paris,  1828. 


264 


CIRCULATION. 


Fig.  8. 


filled  with  mercury,  with  one  arm  bent  at  a  right  angle,  so 
that  it  can  easily  be  connected  with  the  artery.  The  press- 
ure of  the  blood  is  indicated  by  a  depression  in  the  level  of 
the  mercury  on  one  side,  and  a  corresponding  elevation  on 
the  other. 

This  instrument  is  gene^lly  considered  as  possessing 

great  advantages 
over  the  long  glass 
tube;  but  for  esti- 
mating simply  the 
arterial  pressure,  it 
is  much  less  useful, 
as  it  is  more  sensi- 
tive to  the  impulse 
of  the  heart.  For 
the  study  of  the 
cardiac  pressure,  it 
has  the  disadvan- 
tage, in  the  first 
place,  of  consider- 
able friction ;  and 
again,  the  weight 
of  the  column  of 
mercury  produces 
an  extent  of  oscilla- 
tion by  its  mere  im- 
petus, greater  than 
that  which  would 
actually  represent 
the  force  of  the 
heart.1 

An   important 
improvement     in 


Compensating  Instrument  of  Marey. 


1  Ludwig  devised  a  means  of  registering  the  oscillation  in  the  hoemody- 
namometer  of  Poiseuille.  He  used  a  U  tube  of  considerable  size,  and  placed  a 
Coat  on  the  surface  of  the  mercury,  to  which  a  pencil  was  attached  The  point 


AKTEKIAL   PRESSURE.  265 

the  hsemodynamometer  was  made  by  Magendie.  This  ap- 
paratus, the  cardiometer^  in  which  Bernard  has  made  some 
important  modifications,  is  the  one  now  generally  used.  It 
consists  of  a  small  but  thick  glass  bottle,  with  a  fine  graduated 
glass  tube  about  twelve  inches  in  length,  communicating 
with  it,  either  through  the  stopper,  or  by  an  orifice  in  the  side. 
The  stopper  is  pierced  by  a  bent  tube  which  is  to  be  connected 
with  the  blood-vessel.  The  bottle  is  filled  with  mercury  so 
that  it  will  rise  in  the  tube  to  a  point  which  is  marked  zero. 
It  is  evident  that  the  amount  of  pressure  on  the  mercury  in 
the  bottle  will  be  indicated  by  an  elevation  in  the  graduated 
tube ;  and,  moreover,  from  the  fineness  of  the  column  in  the 
tube,  we  avoid  some  of  the  inconveniences  which  are  due  to 
the  weight  of  mercury  in  the  hemodynamometer,  and  also 
have  less  friction. 

This  instrument  is  appropriately  called  the  cardiometer, 
as  it  indicates  most  accurately,  by  the  extreme  elevation  of 
the  mercury,  the  force  of  the  heart ;  but  it  is  not  as  perfect 
in  its  indications  of  the  mean  arterial  pressure,  as  in  the  ab- 
rupt descent  of  the  mercury  during  the  diastole  of  the  heart, 
the  impetus  causes  the  level  to  fall  considerably  below  the 
real  standard  of  the  constant  pressure.  Marey  has  succeeded 
in  correcting  this  difficulty  in  what  he  calls  the  "  compensat- 
ing "  instrument ;  which  is  constructed  on  the  following  prin- 
ciple :  Instead  of  a  simple  glass  tube  which  communicates 
with  the  mercury  in  the  bottle,  as  in  Magendie's  cardiometer, 
he  has  two  tubes :  one  of  which  is  like  the  one  already  describ- 
ed, and  represents  oscillations  produced  by  the  heart ;  the 
other  is  larger,  and  has  at  the  lower  part  a  constriction  of 
the  caliber  which  is  there  reduced  to  capillary  fineness.  This 
tube  is  designed  to  give  the  mean  arterial  pressure.  The 


of  the  pencil,  brought  in  contact  with  a  revolving  cylinder  covered  with  paper, 
produced  a  trace  of  the  oscillations.  By  analysis  of  this  trace  he  arrived  at  the 
mean  pressure  in  the  arteries.  This  instrument  was  called  the  kymographion.  It 
has  never  been  much  used  in  investigation,  and  is  entirely  superseded  by  the  car* 
diometer  of  the  present  day. 


266  CIRCULATION. 

constriction  in  the  tube  offers  such,  an  obstacle  to  the  rise  of 
the  mercury  that  the  intermittent  action  of  the  heart  is  not 
felt,  the  mercury  rising  slowly  to  a  certain  level,  which  is  con- 
stant, and  varies  only  with  the  constant  pressure  in  the  vessels. 

We  have  only  an  approximative  idea  of  the  average  press- 
ure in  the  arterial  system  in  thfc  human  subject,  deduced  from 
experiments  on  animals.  It  has  already  been  stated  to  be 
equal  to  about  six  feet  of  water,  or  six  inches  of  mercury. 

The  most  interesting  questions  connected  with  this  sub- 
ject are :  the  comparative  pressure  in  different  parts  of  the 
arterial  system,  the  influences  which  modify  the  arterial  press- 
ure, and  its  influence  on  the  pulse.  These  points  have  all 
been  pretty  fully  investigated  by  experiments  on  animals,  and 
on  systems  of  elastic  tubes  arranged  to  represent  the  vessels. 

Pressure  in  Different  Parts  of  the  Arterial  System. — 
The  experiments  of  Hales,  Poiseuille,  Bernard,  and  others, 
seem  to  show  that  the  constant  arterial  pressure  does  not  vary 
in  arteries  of  different  sizes.  These  physiologists  have  ex- 
perimented particularly  on  the  carotid  and  crural,  and  have 
found  the  pressure  in  these  two  vessels  about  the  same. 
From  their  experiments,  they  conclude  that  the  force  is 
equal  in  all  parts  of  the  arterial  system.  The  experiments  of 
Yolkmann,  however,  have  shown  that  this  conclusion  has  been 
too  hasty.  With  the  registering  apparatus  of  Ludwig,  he  has 
taken  the  pressure  in  the  carotid  and  metatarsal  arteries,  and 
has  always  found  a  considerable  difference  in  favor  of  the 
former.1  In  an  experiment  on  a  dog,  he  found  the  pressure 

1  For  comparing  the  pressure  in  different  vessels  and  in  different  animals, 
Bernard  has  devised  an  instrument  which  he  calls  the  differentialhcemodynamo- 
meter.  It  consists  of  a  graduated  U  tube  so  arranged  that  both  amis  may  be 
simultaneously  connected  with  separate  vessels.  If  the  pressure  be  equal  in  the 
two  vessels  with  which  it  is  connected,  the  level  of  the  mercury  will  not  be  affect- 
ed ;  but  an  inequah'ty  of  pressure  will  be  marked  by  a  depression  of  the  mercury 
in  the  arm  corresponding  to  the  vessel  in  which  the  pressure  is  the  more  power- 
ful. With  this  instrument,  Bernard  assumes  to  have  demonstrated  that  the  con- 
stant pressure  is  equal  in  all  parts  o€  the  arterial  system,  the  force  of  the  heart, 


ARTERIAL   PRESSURE.  267 

equal  to  172  millimetres  in  the  carotid,  and  165  mm.  in  the 
metatarsal.  In  an  experiment  on  a  calf,  the  pressure  was  116 
mm.  in  the  carotid,  and  89  mm.  in  the  metatarsal ;  and  in  a 
rabbit,  91  mm.  in  the  carotid,  and  86  mm.  in  the  crural.1 

These  experiments,  which  seem  to  have  been  performed 
with  great  care,  show  that  the  pressure  is  not  absolutely  the 
same  in  all  parts  of  the  arterial  system  ;  that  it  is  greatest  in 
the  arteries  nearest  the  heart,  and  gradually  diminishes  as 
we  near  the  capillaries.  The  difference  is  very  slight,  almost 
inappreciable,  until  we  come  to  vessels  of  very  small  size ; 
but  here  the  pressure  is  directly  influenced  by  the  discharge 
of  blood  into  the  capillaries. 

The  cause  of  this  diminution  of  pressure  in  the  smallest 
vessels  is  the  proximity  of  the  great  outlet  of  the  arteries,  the 
capillary  system ;  for,  as  we  shall  see  further  on,  the  flow  into 
the  capillaries  has  a  constant  tendency  to  diminish  the  press- 
ure in  the  arteries.  It  is  obvious  that  this  influence  can  only 
be  felt  in  a  very  marked  degree  in  the  vessels  of  smallest  size.2 

Influence  of  JBespiration. — It  is  easy  to  see,  in  studying 
the  arterial  pressure  with  any  of  the  instruments  we  have 
described,  that  there  is  a  marked  increase  with  expiration, 
and  a  diminution  with  inspiration.  The  fact  that  expiration 
will  increase  the  force  of  the  jet  of  blood  from  a  divided 
artery  has  long  been  observed,  and  accords  perfectly  with  the 
above  statement. 

only,  diminishing  in  the  smaller  vessels.  The  instrument  by  no  means  possesses 
the  delicacy  of  the  apparatus  used  by  Yolkmann,  in  giving  the  mean  pressure. 
(Liquides  de  V  Organisme,  tome  i.,  p.  209  et  seq.) 

1  MILNE-EDWARDS,  op.  tit.,  tome  iv.,  p.  234. 

2  This  view  is  fully  sustained  by  physical  laws.     If  fluid  be  discharged  from  a 
reservoir  by  a  long  horizontal  tube  of  uniform  caliber,  the  pressure,  as  indicated 
by  vertical  tubes  at  different  points,  will  be  found  to  diminish  regularly  from  the 
height  of  the  fluid  in  the  reservoir  to  the  orifice  of  discharge.    An  instrument  of 
this  kind,  which  is  called  a  piezometer,  shows  the  apparent  physical  necessity 
of  a  progressive  diminution  in  pressure  in  the  arterial  system,  as  we  pass  from  the 
heart  to  the  capillaries. 


268  CmCULATTON. 

In  tranquil  respiration,  the  influence  upon  the  flow  of 
blood  is  due  simply  to  the  mechanical  action  of  the  thorax. 
"With  every  inspiration  the  air-cells  are  enlarged,  as  well  as 
the  blood-vessels  of  the  lungs ;  the  air  rushes  in  through  the 
trachea,  and  the  movement  of  the  blood  in  the  veins  near  the 
chest  is  accelerated.  At  the  same  time  the  blood  in  the  arteries 
is  somewhat  retarded  in  its  flow  from  the  thorax,  or  at  least 
does  not  feel  the  expulsive  influence  which  follows  with  the  act 
of  expiration.  The  mean  of  the  arterial  pressure  at  that  time 
is  at  its  minimum.  With  the  expiratory  act,  the  air  is  ex- 
pelled by  compression  of  the  lungs,  the  flow  of  blood  into  the 
thorax  by  the  veins  is  retarded  to  a  certain  extent,  while  the 
flow  of  blood  into  the  arteries  is  favored.  This  is  strikingly 
exhibited  in  the  augmented  force,  with  expiration,  in  the  jet 
from  a  divided  artery.  Under  these  circumstances  the  arte- 
rial pressure  is  at  its  maximum. 

In  perfectly  tranquil  respiration,  the  changes  due  to  in- 
spiration and  expiration  are  very  slight,  marked  by  a  differ- 
ence of  not  more  than  half  an  inch  to  an  inch  in  the  car- 
diometer.  "When  the  respiratory  movements  are  exaggerated, 
the  oscillations  are  very  much  more  marked. 

Interruption  of  respiration  is  followed  by  a  very  great  in- 
crease in  the  arterial  pressure.  This  is  due,  not  to  causes 
within  the  chest,  but  to  obstruction  to  the  circulation  in  the 
capillaries.  We  are  already  aware  of  the  influence  which 
the  flow  of  blood  into  the  capillaries  is  constantly  exerting 
upon  the  arterial  pressure.  This  tendency  to  diminish  the 
quantity  of  blood  in  the  arteries,  and  consequently  the 
pressure,  is  constantly  counteracted  by  the  blood  sent  into 
the  arteries  by  the  contractions  of  the  heart.  In  interruption 
of  the  respiratory  function,  the  non-aerated  blood  passes  into 
the  arteries,  but  refuses  to  pass  through  the  capillaries ;  and 
as  a  consequence,  the  arteries  are  abnormally  distended,  and 
the  arterial  pressure  is  enormously  increased.  If  respiration 
be  permanently  arrested,  the  arterial  pressure  becomes,  after 
a  time,  diminished  below  the  normal  standard,  and  ultimate- 


AKTEEIAL   PEESSUEE.  2(19 

ly  abolished,  on  account  of  the  stoppage  of  the  action  of  the 
heart.  If  respiration  be  resumed  before  the  heart  has  become 
arrested,  the  pressure  soon  returns  to  its  normal  standard. 

Muscular  effort  considerably  increases  the  arterial  press- 
ure. This  is  due  to  two  causes.  In  the  first  place,  the  chest 
is  generally  compressed,  favoring  the  flow  of  blood  into  the 
great  vessels.  In  the  second  place,  muscular  exertion  pro- 
duces a  certain  amount  of  obstruction  to  the  discharge  of 
blood  from  the  arteries  into  the  capillaries.  Numerous  ex- 
periments upon  animals  have  shown  a  great  increase  in  press- 
ure in  the  struggles  which  occur  during  severe  operations. 
Bernard  has  shown  that  galvanization  of  the  sympathetic  in 
the  neck  and  irritation  of  some  of  the  cerebro-spinal  nerves 
increase  the  arterial  pressure,  probably  from  their  effects  on 
the  muscular  coats  of  some  of  the  arteries,  causing  them  to 
contract,  and  thereby  diminishing  the  total  capacity  of  the 
arterial  system.1 

Effects  of  Hemorrhage. — Diminution  in  the  quantity  of 
blood  has  a  remarkable  effect  upon  the  arterial  pressure.  If, 
in  connecting  the  instrument  with  the  arteries,  we  allow  even 
one  or  two  jets  of  blood  to  escape,  the  pressure  will  be  found 
diminished  perhaps  one-half,  or  even  more.  It  is  hardly  neces- 
sary to  discuss  the  mechanism  of  the  effect  of  the  loss  of  blood 
on  the  tension  of  the  vessels,  but  it  is  wonderful  how  soon  the 
pressure  in  the  arteries  regains  its  normal  standard  after  it  has 
been  lowered  by  hemorrhage.  As  it  depends  upon  the  quan- 
tity of  blood,  as  soon  as  the  vessels  absorb  the  serosities  in  suf- 
ficient quantity  to  repair  the  loss,  the  pressure  is  increased. 
This  takes  place  in  a  very  short  time,  if  the  loss  of  blood  be 
not  too  great. 

Experiments  on  the  arterial  pressure  with  the  cardiometer 
have  verified  the  fact  stated  in  treating  of  the  form  of  the  pulse, 
namely,  that  the  pressure  in  the  vessels  bears  an  inverse  ratio 
to  the  distention  produced  by  the  contractions  of  the  heart. 

1  BERNARD,  Liquides  de  VOrganisme,  Paris,  1859,  tome  i.,  p.  241,  et  seq. 


270  CIRCULATION. 

In  the  cardiometer,  the  mean  height  of  the  mercury  indicates 
the  constant,  or  arterial,  pressure,  and  the  oscillations,  the 
distention  produced  by  the  heart.  It  is  found  that  when  the 
pressure  is  great,  the  extent  of  oscillation  is  small,  and  vice. 
versa.  It  will  be  remembered  that  the  researches  of  Marey 
demonstrated  that  an  increase  of  the  arterial  pressure  dimin- 
ishes the  amplitude  of  the  pulsations,  as  indicated  by  the 
sphygmograph,  and  that  the  amplitude  is  very  great  when 
the  pressure  is  slight. 

It  is  also  true,  as  a  general  rule,  that  the  force  of  the  heart, 
as  indicated  by  the  cardiometer,  bears  an  inverse  ratio  to  the 
frequency  of  its  pulsations. 

Summary. — The  arterial  pressure,  due  to  the  distention 
of  the  arteries,  and  the  reaction  of  their  elastic  walls  contin- 
ually forcing  the  blood  toward  the  capillaries,  is  equal  to 
about  six  feet  of  water  or  six  inches  of  mercury.  It  is  in- 
creased by  any  thing  which  favors  the  flow  of  blood  into  the 
great  vessels,  like  the  expiratory  act,  or  by  any  thing  which 
obstructs  the  flow  from  the  arterioles  into  the  capillaries, 
like  muscular  effort,  contraction  of  the  muscular  coat  of  the 
smallest  arteries,  or  non-aeration  of  the  blood.  It  is  dimin- 
ished by  any  considerable  diminution  in  the  quantity  of  the 
circulating  fluid,  or  by  any  thing  which  facilitates  the  passage 
of  blood  through  the  capillaries. 

Rapidity  of  the  Current  of  Blood  in  the  Arteries. 

Though  this  is  not  a  question  of  great  physiological  im- 
portance, it  is  a  point  of  some  interest.  It  has  long  engaged 
the  attention  of  physiologists,  and  has  lately  been  made  the 
subject  of  some  curious  and  ingenious  experiments.  Passing 
over  the  speculations  and  calculations  from  imperfect  physi- 
cal data  of  the  older  physiologists,  which  led  to  no  definite 
results,  we  find  the  first  experiments  on  this  subject  made  by 
Yolkmann,  with  an  instrument  called  the  hemodromometer. 
This  apparatus  consists  of  a  U  tube,  graduated,  and  so  ar- 


RAPIDITY   OF   THE   ARTERIAL   CIRCULATION.  271 

ranged  that  when  the  instrument  is  connected  with  the  artery 
of  a  living  animal,  the  current  may  be  instantaneously  di- 
rected through  the  graduated  tube,  and  by  a  stop-watch,  the 
length  of  time  occupied  in  passing  from  one  extremity  to 
the  other  accurately  measured.  Observations  with  this  in- 
strument, on  the  rapidity  of  the  circulation  in  the  carotid  of 
the  dog  and  horse,  show  that  the  blood  moves  at  the  rate  of 
from  10  to  13  inches  per  second.  The  rapidity  is  diminish- 
ed in  the  smaller  vessels,  being  but  2*2  inches  per  second  in 
the  metatarsal  artery  of  a  horse,  and  10  inches  in  the  carotid.1 

The  results  thus  obtained  cannot  be  received  as  absolutely 
exact.  The  blood  is  diverted  from  its  natural  course,  and 
must  experience  a  certain  diminution  in  velocity  from  the 
curves  in  the  tubes.  It  is  also  evident  that  the  normal  cur- 
rent is  not  uniform  ;  that  it  is  much  more  rapid  immediately 
after  the  systole  of  the  heart,  than  during  the  diastole ;  and, 
as  has  been  demonstrated  by  Marey,  the  blood  in  the  arteries 
undergoes  a  certain  oscillation.  The  experiments  of  Vblk- 
inann  give  an  approximative  idea  of  the  mean  rapidity,  it  is 
true,  but  they  are  far  from  exhibiting  the  natural  current,  with 
the  variations  corresponding  to  the  movements  of  the  heart. 

A  few  years  later  (1858),  an  instrument  was  devised  by 
Yierordt,  which  seemed  to  embody  the  right  principle,  but 
it  was  not  sufficiently  sensitive  to  accomplish  all  that  was  de- 

1  The  experiments  of  Volkmann  and  Huttenheim,  published  in  1846,  are  re- 
ferred to,  and  the  instrument  described  and  delineated,  in  most  works  on  physiol- 
ogy. When  the  instrument  is  first  connected  with  the  artery,  the  blood  passes 
through  a  straight  tube,  and  is  not  deviated  from  its  course.  The  current  is 
diverted  into  the  graduated  U  tube  by  two  stop-cocks  which  are  arranged  so  that 
they  may  be  turned  simultaneously.  Before  it  is  applied,  the  apparatus  is  filled 
with  warm  water,  so  as  to  prevent  the  entrance  of  air  into  the  vessels. 

The  following  are  the  results  obtained  by  Volkmann  in  experiments  on  dogs 
and  horses : 

In  the  dog,  carotid        .         .         .         .         10 '7  inches  per  second. 

do.  do.          ....         13        u         "         " 

In  the  horse,  carotid  10        "         "         " 

do.  raetatarsal  artery      .         .  2-2.    "         "         " 

— LONGET,  Traite  de  Physiologic,  Paris,  1861,  tome  L,  p.  848. 


272  CIRCULATION. 

sired.  It  consisted  of  a  little  square  box  made  of  glass,  with 
an  opening  at  each,  end,  by  which  it  was  to  be  connected  with 
the  artery.  This  is  filled  with  water,  and  contains  a  pendu- 
lum, which  is  struck  by  the  current  of  blood.  The  deviations 
of  the  pendulum  are  marked  on  a  scale.  After  this  has 
been  applied  to  an  artery,  and  the  extent  of  movement  of 
the  pendulum  noted,  it  is  removed  from  the  vessel  and  con- 
nected with  an  elastic  tube,  in  which  a  current  of  water  is 
made  to  pass  with  a  degree  of  rapidity  which  will  produce 
the  same  deviation  as  occurred  when  the  instrument  was  con- 
nected with  the  blood-vessel.  The  rapidity  of  the  current  in. 
this  tube  may  be  easily  calculated  by  receiving  the  fluid  in  a 
graduated  vessel,  and  noting  the  time  occupied  in  discharg- 
ing a  given  quantity.  By  this  means  we  ascertain  the 
rapidity  of  the  current  of  blood.  By  means  of  a  needle 
attached  to  the  pendulum,  the  oscillations  could  be  regis- 
tered on  a  revolving  cylinder  of  paper,  and  the  mean  velocity 
taken. 

With  this  instrument,  Yierordt  estimated  the  mean  velo- 
city of  blood  in  the  carotid  at  10*2  inches  per  second.  Chau- 
veau,  who  invented  an  instrument  which  we  will  describe 
presently,  found  the  instrument  of  Yierordt  not  sufficiently 
sensitive,  and  requiring  so  much  care  and  precaution  in  its 
use  as  to  essentially  diminish  the  value  of  its  results. 

The  best  instrument  for  measuring  the  rapidity  of  the 
circulation  in  the  arteries  was  devised  by  Chauveau,  of  the 
Yeterinary  School  at  Lyons.1  This  will  give,  by  calcula- 
tion, the  actual  rapidity  of  the  circulation  ;  and,  what  is  more 
interesting,  it  marks  accurately  the  rapid  variations  in  velo- 
city, with  reference  to  the  heart's  action. 

The  instrument  to  be  applied  to  the  carotid  of  the 
horse  consists  of  a  thin  brass  tube,  about  1J  inch  in  length, 
and  of  the  diameter  of  the  artery  (about  f  of  an  inch),  which  is 

1  MM.  A.  CHAUYEAU,  G.  BERTOLUS  et  L.  LAROYENNE,  Vitesse  de  la  Circulation 
dam  les  Arteres  du  Cheval.— Journal  de  la  Physiologic,  Paris,  1860,  tome  iii., 
p.  695. 


RAPIDITY  OF   THE   AKTEKIAL   CIRCULATION. 


273 


Fig.  9. 


provided  with  an 
oblong  longitudi- 
nal opening,  or 
window,  near  the 
middle,'  about  two 
lines  long  and  one 
line  wide.  A 
piece  of  thin  vul- 
canized rubber  is 
wound  around  the 
tube,  and  firmly 
tied,  so  as  to  cov- 
er this  opening. 
Through  a  trans- 
verse slit  in  the 
rubber  is  intro- 
duced a  very  light 

metallic       needle,Chauveau's  instrument  for  measuring  the  rapidity  of  the  flow  of 
•i  ITT/?    blood  in  the  arteries.    The  instrument  viewed  in  face — a,  the 

an  men  and  a  nail  tube  to  be  fixed  in  the  vessel;  &,  the  dial  which  marks  the  ex- 
•  -i  , -i  T  n  ,  tent  of  movement  of  the  needle  d ;  *,  a  lateral  tube  for  the 

111  length,  aild  fiat-    attachment  of  a  cardiometer,  if  desired. 

tened  at  its  lower  part.  This  is  made  to  project  about  half 
way  into  the  caliber  of  the  tube.  A  flat  semicircular  piece 
of  metal,  divided  into  an  arbitrary  scale,  is  attached  to  the 
tube,  to  indicate  the  deviations  of  the  point  of  the  needle. 

The  apparatus  is  introduced  carefully  into  the  carotid  of 
a  horse,  by  making  a  slit  in  the  vessel,  introducing  first  one 
end  of  the  tube,  directed  toward  the  heart,  then  allowing  a 
little  blood  to  enter  the  instrument,  so  as  to  expel  the  air, 
and,  when  full,  introducing  the  other  end,  securing  the  whole 
by  ligatures  above  and  below. 

When  the  circulation  is  arrested,  the  needle  should  be 
vertical,  or  mark  zero  on  the  scale.  "When  the  flow  is  estab- 
lished, a  deviation  of  the  needle  occurs,  which  varies  in  extent 
with  the  rapidity  of  the  current. 

Having  removed  all  pressure  from  the  vessel,  so  as  to  al- 
low the  current  to  resume  its  normal  character,  the  deviations 
18 


274:  CIRCULATION. 

of  the  needle  are  carefully  noted,  as  they  occur  with  the  sys- 
tole of  the  heart,  with  the  diastole,  etc.  After  withdrawing 
the  instrument,  it  is  applied  to  a  tube  of  the  size  of  the  ar- 
tery, and  we  measure  the  rapidity  of  the  current  required  to 
carry  the  needle  to  the  points  noted,  which  may  be  done  by 
the  same  calculation  used  in  graduating  the  apparatus  of 
Yierordt.1 

This  instrument  is  on  the  same  principle  as  the  one  con- 
structed by  Yierordt,  but  in  sensitiveness  and  accuracy  is 
much  superior.  In  the  hands  of  Chauveau,  the  results,  par- 
ticularly those  with  regard  to  variations  in  the  rapidity  of 
the  current,  are  very  interesting. 

Rapidity  of  the  Current  in  the  Carotid. — It  has  been 
found  that  three  currents,  with  different  degrees  of  rapidity, 
may  be  distinguished  in  the  carotid : 

1.  At  each  ventricular  systole,  we  have,  as  the  average 
of  the  experiments  of  Chauveau,  the  blood  moving  in  the 
carotids  at  the  rate  of  twenty  -^  inches  per  second.     After 
this  the  rapidity  quickly  diminishes,  the  needle  returning 
quite   or  nearly  to  zero,  which  would  indicate   complete 
arrest. 

2.  Immediately  succeeding  the  ventricular  systole,  we  have, 
a  second  impulse  given  to  the  blood,  which  is  synchronous 
with  the  closure  of  the  semilunar  valves,  the  blood  moving 
at  the  rate  of  eight  -^  inches  per  second.     This  Chauveau 
calls  the  dicrotic  impulse. 

3.  After  the  dicrotic  impulse,  the  rapidity  of  the  current 
gradually  diminishes,  until,  just  before  the  systole  of  the 
heart,  it  becomes  almost  nil.     The  average  rate  after  the  di- 
crotic impulse  is  five  -f$  inches  per  second. 

These  experiments  give  us,  for  the  tirst  time,  correct  no- 
tions of  the  rapidity  and  variations  of  the  flow  of  blood  in 
the  larger  vessels ;  and  it  is  seen  that  they  correspond  in  a 

1  In  graduating  the  apparatus,  Chauveau  uses  warm  water.    It  would  be 
more  accurate  to  use  defibrinated  blood,  or  a  fluid  of  equal  density. 


RAPIDITY   OF  THE   ARTERIAL   CIRCULATION,  275 

remarkable  degree  with  the  experiments  of  Marej  on  the 
form,  of  the  pulse.  Marey  showed  that  there  is  a  marked  os- 
cillation of  the  blood  in  the  vessels,  due  to  a  reaction  of  their 
elastic  walls,  following  the  first  violent  distention  by  the 
heart ;  that  at  the  time  of  closure  of  the  semilunar  valves,  the 
arteries  experience  a  second,  or  dicrotic,  distention,  much  less 
than  the  first ;  and  following  this,  there  is  a  gradual  decline 
in  the  distention  until  the  minimum  is  reached.  Chauveau 
shows  by  experiments  with  his  instrument,  that  correspond- 
ing to  the  first  dilatation  of  the  vessels,  the  blood  moves  with 
immense  rapidity ;  following  this,  the  current  suddenly  be- 
comes nearly  arrested ;  this  is  followed  by  a  second  accelera- 
tion in  the  current,  less  than  the  first;  and  following  this  we 
have  a  gradual  decline  in  the  rapidity  to  the  time  of  the  next 
pulsation. 

Rapidity  in  Different  Parts  of  the  Arterial  System. — 
From  the  fact  that  the  arterial  system  increases  in  capacity 
as  we  recede  from  the  heart,  we  should  expect  to  find  a  cor- 
responding diminution  in  the  rapidity  of  the  flow  of  blood. 
There  are,  however,  many  circumstances,  aside  from  simple 
increase  in  the  capacity  of  the  vessels,  which  undoubtedly 
modify  the  blood  current,  and  render  inexact  any  calculations 
on  purely  physical  principles ;  such  as  the  tension  of  the 
blood,  the  conditions  of  contraction  or  relaxation  of  the 
smallest  arteries,  etc.  It  is  therefore  necessary  to  have  re- 
course to  actual  experiment  to  arrive  at  any  definite  results 
on  this  point.  The  experiments  of  Volkmann  showed  a  great 
difference  in  the  rapidity  of  the  current  in  the  carotid  and 
metatarsal  arteries,  the  average  being  10  inches  per  second 
in  the  carotid,  to  2*2  inches  in  the  metatarsal.  The  same 
difference,  though  not  quite  as  marked,  was  found  by  Chau- 
veau between  the  carotid  and  the  facial. 

The  last-named  observer  also  noted  an  important  modifi- 
cation in  the  character  of  the  current  in  the  smaller  vessels. 
As  we  recede  from  the  central  organ,  the  systolic  impulse 


276  CIRCULATION. 

becomes  rapidly  diminished,  being  reduced  in  one  experiment 
about  two-thirds ;  the  dicrotic  impulse  becomes  very  feeble  or 
even  abolished ;  but  the  constant  flow  is  very  much  increased 
in  rapidity.  This  fact  coincides  with  the  ideas  already  ad- 
vanced, with  regard  to  the  gradual  conversion,  by  virtue  of 
the  elasticity  of,  the  vessels,  of  the  impulse  of  the  heart  into, 
first,  a  remittent,  and,  in  the  very  smallest  arteries,  a  nearly 
constant  current. 

The  rapidity  of  the  flow  in  any  artery  must  be  subject  to 
constant  modifications  due  to  the  condition  of  the  arterioles 
which  are  supplied  by  it.  When  these  little  vessels  are  di- 
lated, the  artery  of  course  empties  itself  with  greater  facility, 
and  the  rapidity  is  increased.  Thus  the  rapidity  bears  a  re- 
lation to  the  arterial  pressure ;  as,  independently  of  a  dimi- 
nution in  the  entire  quantity  of  the  circulating  fluid,  varia- 
tions in  the  pressure  depend  chiefly  on  causes  which  facili- 
tate or  retard  the  flow  of  blood  into  the  capillaries.  A  good 
example  of  enlargement  of  the  capillaries  of  a  particular  part, 
is  in  mastication,  when  the  salivary  glands  are  brought  into 
activity,  and  the  quantity  of  blood  which  they  receive  is 
greatly  increased.  Chauveau  found  an  immense  increase  in 
the  rapidity  of  the  flow  in  the  carotid  of  a  horse  during  mas- 
tication. The  enlargement  of  the  vessels  of  the  glands  during 
their  function  has  been  conclusively  proven  by  the  experi- 
ments of  Bernard. 

It  must  be  remembered  that  in  all  parts  of  the  arterial 
system  the  rapidity  of  the  current  of  blood  is  constantly  liable 
to  increase  from  dilatation  of  the  small  vessels,  and  diminution 
from  their  contraction. 

Arterial  Murmurs. 

In  the  largest  vessels,  we  can  frequently  hear  with  the 
stethoscope  the  sounds  conducted  from,  the  heart.  In  addi- 
tion, we  can  hear,  in  all  except  the  smallest  vessels,  a  pecu- 
liar blowing  sound,  called  the  fyruit  de  souffle,  which  is 


AETERIAL   MURMURS.  277 

produced  by  the  pressure  of  the  end  of  the  instrument  on  the 
artery.  The  following  is  the  mechanism  of  the  production 
of  this  sound :  The  pressure  of  the  instrument  produces  a 
constriction  in  the  vessel,  and  more  or  loss  obstruction  to  the 
current  of  blood.  As  the  blood  flows  from  this  constricted  por- 
tion into  that  just  beyond,  where  of  course  the  vessel  is  rela- 
tively larger  and  the  current  is  somewhat  retarded,  the  rela- 
tively small  and  forcible  stream  produces  an  unusual  and 
irregular  current,  which  is  accompanied  by  a  certain  sound. 
It  has  been  proven  by  the  experiments  of  Chauveau  and 
Marey  with  elastic  tubes,  that  this  sound  is  always  produced 
when  any  part  of  the  apparatus  is  dilated  so  that  the  fluid 
passes  from  the  tube  into  a  sort  of  sac.  In  this  way  aneuris- 
mal  murmurs  are  accounted  for.  The  sounds  which  are 
heard  in  the  arteries,  and  are  not  dependent  upon  compres- 
sion with  the  stethoscope,  depend  upon  conditions,  the  con- 
sideration of  which  belongs  to  pathology. 


CHAPTEE  VII. 

CIRCULATION   OF   THE   BLOOD   IN   THE    CAPILLAEIES. 

Distinction  between  capillaries  and  the  smallest  arteries  and  veins — Physiological 
anatomy  of  the  capillaries — Peculiarities  of  distribution — Capacity  of  the 
capillary  system — Course  of  blood  in  the  capillaries — Phenomena  of  the 
capillary  circulation — Rapidity  of  the  capillary  circulation — Relations  of  the 
capillary  circulation  to  respiration — Causes  of  the  capillary  circulation — In- 
fluence of  temperature  on  the  capillary  circulation — Influence  of  direct  irrita- 
tion on  the  capillary  circulation. 

BEFOBE  entering  upon  the  study  of  the  capillary  circu- 
lation, let  us  define  what  we  mean  by  the  capillary  vessels, 
as  distinguished  from  the  smallest  arteries  and  veins.  From 
a  strictly  physiological  point  of  view,  the  capillaries  should 
be  regarded  as  commencing  at  the  point  where  the  blood  is 
brought  near  enough  to  the  tissues,  to  enable  them  to  sep- 
arate the  elements  necessary  for  their  regeneration,  and  give 
up  the  products  of  their  physiological  decay.  With  our 
present  knowledge,  it  is  impossible  to  assign  any  limit  where 
the  vessels  cease  to  be  simple  carriers  of  blood ;  and  it  does 
not  seem  probable  that  it  will  ever  be  known  to  what  part  of 
the  vascular  system  the  processes  of  nutrition  are  exclusively 
confined.  The  divisions  of  the  blood-vessels  must  be,  to  a 
certain  extent,  arbitrarily  defined,  and  we  should  feel  at  lib- 
erty to  adopt  the  views  of  any  reliable  observer  with  regard 
to  the  kind  of  vessels  which  are  to  be  considered  as  capilla- 
ries. The  most  simple,  and  what  seems  to  be  the  most  phys- 


PHYSIOLOGICAL   ANATOMY   OF  THE   CAPILLARIES.  279 

iological  view,  is  that  the  capillaries  are  the  vessels  which 
have  but  a  single,  homogeneous  tunic ;  for  in  these  the  blood 
is  brought  in  closest  proximity  to  the  tissues.  Vessels  which 
are  provided,  in  addition,  with  a  muscular,  or  muscular  and 
fibrous  coats,  are  to  be  regarded  as  either  small  arteries,  or 
venous  radicles.  This  view  is  favored  by  the  character  of 
the  currents  of  blood,  as  seen  in  microscopic  observations  on 
the  circulation  in  transparent  parts.  Here  an  impulse  is 
observed  with  each  contraction  of  the  heart,  until  we  come 
to  vessels  which  have  but  a  single  coat,  and  are  so  narrow  as 
to  allow  the  passage  of  but  a  single  line  of  blood-corpuscles. 

Physiological  Anatomy  of  the  Capillaries. — If  the  arteries 
be  followed  out  to  their  minutest  ramifications,  they  will  be 
found  progressively  diminishing  in  size  as  they  branch,  and 
their  coats,  especially  the  muscular,  becoming  thinner  and 
thinner,  until  at  last  they  present  an  internal  structureless 
coat,  provided  with  oval  longitudinal  nuclei ;  a  middle  coat 
formed  of  but  a  single  layer  of  circular  muscular  fibres,  the 
oval  nuclei  of  which  are  at  right  angles  to  the  nuclei  of  the 
internal  coat ;  and  an  external  coat  composed  of  a  very  thin 
layer  of  longitudinal  fibres  of  the  white  inelastic  tissue.  Kobin 
calls  these  the  third  variety  of  capillary  vessels ;  but  they  are 
large,  -j-J-Q-  to  -g-J-g-  of  an  inch  in  diameter,  become  smaller  as 
they  branch,  and  undoubtedly  possess  the  property  of  con- 
tractility, which  is  particularly  marked  in  the  arterial  system. 
Following  the  course  of  the  vessels,  when  they  are  reduced  in 
size  to  about  -g-J-Q-  of  an  inch,  the  external  fibrous  coat  is  lost, 
and  the  vessel  then  presents  only  the  internal  structureless 
coat,  and  the  single  layer  of  muscular  fibres.  These  are 
called  by  Kobin,  capillaries  of  the  second  variety.  They 
become  smaller  as  they  branch,  and  finally  lose  the  muscular 
coat,  and  have  then  but  the  single  amorphous  tunic,  with  its 
longitudinal  nuclei.  These,  the  capillaries  of  the  first  variety 
of  Robin,1  we  shall  consider  as  the  true  capillary  vessels. 

1  Didionnaire  de  Medecine,  etc.,  Paris,  1858  (Capillaire).    This  division  of  the 


280  CIRCULATION. 

The  true  capillary  vessels  present  the  following  charac- 
teristics : 

1.  Simplicity  of  Structure. — They  have  but  the  single 
amorphous  coat,  from  -g-yJor  to  TirVoT  °f  an  incn  thick,  the 
continuation  of  the  lining  membrane  of  the  larger  vessels ; 
not  provided  with  an  epithelial  lining,  but  presenting,  im- 
bedded in  its  thickness,  a  number  of  oval  nuclei  with  their 
long  diameters  in  the  direction  of  the  axis  of  the  vessel. 

2.  Small  Diameter  of  the  Vessels. -^Their  diameter  is  gen- 
erally as  small  or  smaller  than  that  of  the  blood-corpuscles ; 
so  that  these  bodies  always  move  in  a  single  line,  and  must 
become  deformed  in  passing  through  the  smallest  vessels ; 
recovering  their  natural  shape,  however,  when  they  pass  into 
vessels  of  larger  size.     The  capillaries  are  smallest  in  the 
nervous  and  muscular  tissue,  retina,  and  patches  of  Peyer, 
where  they  have  a  diameter  of  from  -g^Vo-  to  ^^  of  an  inch. 
In  the  mucous  layer  of  the  skin,  and  in  the  mucous  mem- 
branes, they  are  from  ^Vo-  t°  -nVir  °f  an  ^ncn  ^n  diameter. 
They  are  largest  in  the  glands  and  bones,  where  they  are  from 
g^—  to  -joVu  °f  an  inch  in  diameter.1     These  measurements 
indicate  the  size  of  the  vessel,  and  not  its  caliber.     Taking 
.out  the  thickness  of  their  walls,  it  is  only  the  very  largest  of 
them  which  will  admit  of  the  passage  of  a  blood-disk  without 
,a  change  in  its  form. 

3.  Peculiarities  of  Distribution. — Unlike  the  arteries, 
which  grow  smaller  as  they  branch,  and  simply  carry  blood 
by  the  shortest  course  to  the  parts,  and  the  veins,  which  be- 
come larger  as  we  follow  the  course  of  the  blood  by  union 
with  each  other,  the  capillaries  form  a  true  plexus  of  vessels 
of  nearly  uniform  diameter,  branching  and  inosculating  in 

capillaries  into  three  varieties,  the  first  with  a  homogeneous  coat,  the  second  with 
the  addition  of  the  muscular  coat,  and  the  third  with  the  muscular  and  fibrous 
coat,  was  made  by  Henle,  and  is,  perhaps,  the  one  most  generally  adopted.  Kol- 
liker  gives  the  division  we  have  adopted,  regarding  as  true  capillaries  only  those 
vessels  which  have  a  single  coat.  The  others  he  calls  "vessels  of  transition." 
1  KOLLIKER,  Manual  of  Human  Microscopic  Anatomy,  London,  1860,  p.  500, 


PHYSIOLOGICAL  ANATOMY   OF   THE   CAPILLARIES.  281 

every  direction,  distributing  blood  to  the  parts,  as  their  phys- 
iological necessities  demand.  This  inosculation  is  peculiar 
to  these  vessels,  and  the  plexus  is  rich  in  the  tissues,  as  a  gen- 
eral rule,  in  proportion  to  the  activity  of  their  nutrition. 
Though  their  arrangement  presents  certain  differences  in 
different  organs,  the  capillary  vessels  have  everywhere  the 
same  general  characteristics,  the  most  prominent  of  which 
are  uniform  diameter  and  absence  of  any  positive  direction. 

The  network  thus  formed  is  very  rich  in  the  substance 
of  the  glands,  and  in  the  organs  of  absorption  ;  but  the  ves- 
sels are  only  distended  with  blood  during  the  physiological 
activity  of  these  parts.  In  the  lungs  the  meshes  are  partic- 
ularly close.  In  other  parts  the  vessels  are  not  so  abundant, 
presenting  great  variations  in  different  tissues.  In  the  mus- 
cles and  nerves,  in  which  nutrition  is  very  active,  the  supply 
is  much  more  abundant  than  in  other  parts,  like  nbro-serous 
membranes,  tendons,  etc.,  whose  functions  are  rather  passive.1 
In  none  of  the  tissues  do  we  find  capillaries  penetrating  the 
anatomical  elements,  as  the  ultimate  muscular  or  nervous 
fibres.  Some  tissues  receive  no  blood,  at  least  they  contain 
no  vessels  which  are  capable  of  carrying  red  blood,  and  are 
nourished  by  imbibition  of  the  nutrient  plasma  of  the  circu- 
lating fluid.  Examples  of  these,  which  are  called  extra-vas- 
cular, are  cartilage,  nails,  hair,  etc. 

The  foregoing  anatomical  sketch  gives  an  idea  of  how 
near  the  blood  is  brought  to  the  tissues  in  the  capillary  sys- 
tem, and  how,  once  conveyed  there  by  the  arteries,  and  the 
supply  regulated  by  the  action  of  the  muscular  coat  of  the 
smaller  vessels,  the  blood  is  distributed  for  the  purposes  of 
nutrition,  secretion,  absorption,  exhalation,  or  whatever  func- 

1  The  arrangement  of  the  capillaries  in  different  tissues  and  organs  has  gen- 
erally been  ascertained  by  minute  injections.  In  studying  injected  preparations, 
however,  it  must  be  borne  in  mind  that  when  injected,  the  elastic  and  yielding 
vessels  are  distended  to  their  extreme  capacity,  and  the  capillaries,  therefore, 
occupy  a  space  much  greater  than  is  natural.  In  injections  of  the  liver,  for  ex- 
ampJe,  the  capillaries  seem  to  constitute  the  bulk  of  the  organ,  and  we  are  at  a 
'oss  to  understand  how  the  cells,  ducts,  etc.,  find  place  between  their  meshes. 


282  CIRCULATION. 

tion  the  part  has  to  perform.  This  will  be  still  more  appa- 
rent when  we  come  to  consider  the  course  of  the  blood  in  the 
capillaries,  and  the  immense  capacity  of  this  system,  as  com- 
pared with  the  arteries  or  veins. 

The  capacity  of  the  capillary  system  is  immense.  It  is 
only  necessary  to  consider  the  prodigious  vascularity  of  the 
skin,  mucous  membranes,  or  muscles,  to  realize  this  fact.  In 
injections  of  these  parts,  it  seems,  on  microscopic  examination, 
as  though  they  contained  nothing  but  capillaries.  In  prepa- 
rations of  this  kind,  the  elastic  and  yielding  coats  of  the  capil- 
laries are  distended  to  their  utmost  limit.  Under  some  cir- 
cumstances, in  health,  they  are  much  distended  with  blood, 
as  the  mucous  lining  of  the  alimentary  canal  during  diges- 
tion, the  whole  surface  presenting  a  vivid  red  color,  indicat- 
ing the  great  richness  of  the  capillary  plexus.  Various 
estimates  of  the  capacity  of  the  capillary,  as  compared  with 
the  arterial  system,  have  been  made,  but  they  are  simply  ap- 
proximative, and  there  seems  to  be  no  means  by  which  an 
estimate,  with  any  pretentious  to  accuracy,  can  be  formed. 
The  various  estimates  which  are  given  are  founded  upon  cal- 
culations from  microscopic  examinations  of  the  rapidity  of 
the  capillary  circulation,  as  compared  with  the  arteries.  In 
this  way  Bonders  estimates  the  entire  capacity  of  the  capil- 
lary system  as  500,  and  Yierordt  as  800  times  that  of  the 
arterial  system.  It  must  be  evident  to  any  one  who  has 
witnessed  the  capillary  circulation  under  the  microscope,  that 
the  conditions  under  which  the  animal  under  examination  is 
placed  are  liable  to  interfere  with  the  current  of  blood ;  and 
the  periodical  congestion  of  certain  parts,  the  fugitive  flushes 
of  the  skin,  the  condition  of  the  smallest  arteries  induced  by 
changes  of  temperature,  exercise,  etc.,  make  it  evident  that 
the  current  of  blood  is  liable  to  great  variations.  It  is  impos- 
sible to  strictly  apply  to  the  capillary  circulation  in  the  vari- 
ous parts  of  the  human  subject,  observations  on  the  wing  of  a 
bat,  or  the  mesentery  of  a  cat.  We  must  consider,  then, 


COURSE   OF  BLOOD  IN  THE   CAPILLARIES.  283 

these  estimates  as  mere  suppositions ;  and  they  are  given  for 
what  they  are  worth. 

With  the  older  physiologists,  the  contractility  of  the  capil- 
laries was  a  subject  of  discussion.  Some  went  so  far  as  to 
suppose  that  these  little  vessels  were  the  seat  of  rhythmical 
contractions  which  materially  assisted  the  flow  of  the  blood.  In 
microscopic  examinations,  irritation  or  stimulation  is  seen  to 
produce  contraction  of  the  smallest  arteries ;  but  there  is  no 
evidence  that  the  capillaries,  which  have  a  single  amorphous 
coat,  have  any  such  property.  They  undergo,  while  under 
observation,  considerable  alterations  in  caliber;  but  this  is 
due,  in  all  probability,  to  differences  in  the  pressure  of  blood 
in  their  interior.  The  capillaries  can  only  be  considered  as 
endowed  with  elasticity,  which  enables  them  to  react  upon 
their  contents,  when  there  is  any  diminution  in  pressure.  In 
the  vascular  system,  contractility  disappears  with  the  muscu- 
lar fibre- cells  which  form  the  middle  coat  of  the  arterioles. 

Course  of  the  Blood  in  the  Capillaries. 

The  phenomena  of  the  capillary  circulation  are  only  ob- 
servable with  the  aid  of  the  microscope.  It  was  not  granted 
to  the  discoverer  of  the  circulation  to  see  the  blood  moving 
through  the  capillaries,  and  he  never  knew  the  exact  mode 
of  communication  between  the  arteries  and  veins.  After  it 
was  pretty  generally  acknowledged  that  the  blood  did  pass 
from  the  arteries  to  the  veins,  it  was  disputed  whether  it 
passed  in  an  intermediate  system  of  vessels,  or  became  dif- 
fused in  the  substance  of  the  tissues,  like  a  river  flowing 
between  numberless  little  islands,  to  be  collected  by  the  ve- 
nous radicles  and  conveyed  to  the  heart.  Accurate  micro- 
scopic investigations  have  now  demonstrated  the  existence, 
and  given  us  a  clear  idea  of  the  anatomy,  of  the  interme- 
diate vessels.  In  1661,  the  celebrated  anatomist,  Malpighi, 
first  saw  the  movement  of  the  blood  in  the  capillaries,  in  the 
lungs  of  a  frog.  Since  that  time,  physiologists  have  studied 


284:  CIRCULATION. 

the  circulation  in  various  transparent  parts  in  the  inferior 
animals,  as  the  web  of  the  frog's  foot,  the  tongue  of  the  frog, 
the  lungs  of  the  frog  and  of  the  water-newt,  tile  mesentery  of 
very  young  rats  or  mice,  the  wing  of  the  bat,  etc.  The  most 
convenient  situation  is  the  tongue  or  the  web  of  the  frog. 
Here  may  be  studied,  not  only  the  movement  of  the 
blood  in  the  true  capillaries,  but  the  circulation  in  the  small- 
est arteries  and  veins ;  the  variations  in  caliber  of  these  ves- 
sels, especially  the  arterioles,  by  the  action  of  their  muscular 
tunic;  and  indeed  the  action  of  vessels  of  considerable 
size.  This  has  been  a  most  valuable  means  of  studying  the 
circulation  in  the  capillaries,  as  contrasted  with  the  small 
arteries  and  veins ;  the  only  one,  indeed,  which  could  give  us 
any  definite  idea  of  the  action  of  these  vessels. 

Before  taking  up  the  causes  of  the  capillary  circulation, 
and  the  various  physical  or  vital  laws  which  are  involved,  we 
will  describe  the  phenomena  which  are  observed  with  the  aid 
of  the  microscope. 

Phenomena  of  the  Capillary  Circulation. — The  magnifi- 
cent spectacle  of  the  capillary  circulation,  first  observed  by 
Malpighi,  in  the  lungs,  and  afterwards  by  Leeuwenhoek, 
Spallanzani,  Haller,  Cowper,  and  others,  in  other  parts,  has 
ever  since  been  the  delight  of  the  physiologist.  "We  see 
the  great  arterial  rivers,  in  which  the  blood  flows  with  won- 
derful rapidity,  branching  and  subdividing,  until  the  blood  is 
brought  to  the  superb  network  of  fine  capillaries,  where  the 
corpuscles  dart  along  one  by  one ;  the  fluid  being  then  col- 
lected by  the  veins,  and  carried  in  great  currents  to  the  heart. 
This  exhibition,  to  the  student  of  Nature,  is  of  inexpressible 
grandeur;  and  our  admiration  is  not  diminished  when  we 
come  to  study  the  phenomena  in  detail.  "We  find  here  a 
subject  as  interesting  as  was  the  action  of  the  heart  when  first 
seen  by  Harvey,  involving  some  of  the  most  important  phe- 
nomena of  the  circulation.  It  can  be  seen  how  the  arterioles 
regulate  the  supply  of  blood  to  the  tissues ;  how  the  blood 


PHENOMENA   OF   THE   CAPILLARY   CIRCULATION.  285 

distributes  itself  by  the  capillaries  ;  and  finally,  having  per- 
formed its  office,  how  it  is  collected  and  carried  off  by  the 
veins.1 

In  studying  the  circulation  under  the  microscope,  the  an- 
atomical division  of  the  blood  into  corpuscles  and  a  clear 
plasma  is  observed.  This  is  peculiarly  evident  in  cold-blood- 
ed animals,  the  corpuscles  being  comparatively  large,  and 
floating  in  a  plasma  which  forms  a  distinct  layer  next  the 
walls  of  the  vessel.  The  white  corpuscles,  which  are  much 
fewer  than  the  red,  are  generally  found  in  the  layer  of 
plasma. 

In  vessels  of  considerable  si^e,  as  well  as  the  capillaries, 
the  corpuscles,  occupying  the  central  portion,  move  with 
much  greater  rapidity  than  the  rest  of  the  blood,  leaving  a 
layer  of  clear  plasma  at  the  sides,  which  is  nearly  immovable. 
This  curious  phenomenon  is  in  obedience  to  a  physical  law 
regulating  the  passage  of  liquids  through  capillary  tubes  for 
which  they  have  an  attraction,  such  as  exists,  for  example, 
between  the  blood  and  the  vessels.  In  tubes  reduced  to  a 
diameter  approximating  to  that  of  the  capillaries,  the  attractive 
force  exerted  by  their  walls  upon  a  liquid,  causing  it  to  enter 

1  Various  methods  of  preparing  the  animal  for  examination  have  been  em- 
ployed. The  one  we  have  found  most  convenient,  in  examining  the  circulation 
in  the  frog,  is  to  break  up  the  medulla  with  a  needle,  an  operation  which  does  not 
interfere  with  the  circulation,  and  attach  the  animal  by  pins  to  a  thin  piece  of 
cork,  stretching  the  web  over  an  orifice  hi  the  cork,  to  allow  the  passage  of  light, 
and  securing  it  with  phis  through  the  toes.  The  membrane  is  then  moistened  with 
water,  and  covered  with  thin  glass,  and  if  the  general  surface  be  kept  moist,  the 
circulation  may  be  studied  for  hours.  (See  "  Phenomena  of  the  Capillary  Circula- 
tion," an  inaugural  thesis,  by  the  author,  American  Journal  of  the  Medical  Sciences, 
July,  1857.)  By  gently  inflating  the  lungs  with  a  small  blow-pipe,  securing  them 
by  a  ligature  passed  around  the  larynx  beneath  the  mucous  membrane,  and  open- 
ing the  chest,  the  circulation  may  be  examined  in  this  situation.  It  may  be  stu- 
died in  the  tongue  (which  presents  a  magnificent  view  of  the  circulation  as  well  as 
the  nerves  and  muscular  fibres)  by  drawing  it  out  of  the  mouth,  and  spreading  it 
into  a  thin  sheet,  securing  it  with  pins.  The  circulation  may  be  studied  in  the 
mesentery  of  a  small  warm-blooded  animal,  like  the  mouse,  by  fixing  it  upon  the 
frog-plate,  opening  the  abdomen,  and  drawing  out  the  membrane ;  but  not  as 
well  or  as  conveniently  as  in  the  tongue  or  web  of  the  frog. 


2  86  CIRCULATION. 

the  tube  to  a  certain  distance,  called  capillary  attraction,  be- 
comes an  obstacle  to  the  passage  of  fluid  in  obedience  to 
pressure.  Of  course,  as  the  diameter  of  the  tube  is  reduced, 
this  force  becomes  relatively  increased,  for  a  larger  propor- 
tion of  the  liquid  contents  is  brought  in  contact  with  it. 
When  we  come  to  the  smallest  arteries  and  veins,  and  still 
more  the  capillaries,  the  capillary  attraction  is  sufficient  to 
produce  the  immovable  layer,  called  the  "  still  layer "  by 
many  physiologists,  and  the  liquid  only  moves  in  the  central 
portion.  The  plasma  occupies  the  position  next  the  walls  of 
the  vessels,  for  it  is  this  portion  of  the  blood  which  is  capable 
of  wetting  the  tubes.  The  transparent  layer  was  observed 
by  Malpighi,  Haller,  and  all  who  have  described  the  capillary 
circulation.  Poiseuille  recognized  its  true  relation  to  the 
blood -current,  and  explained  the  phenomenon  of  the  still 
layer  by  physical  laws,  which  had  been  previously  established 
with  regard  to  the  flow  of  liquids  in  tubes  of  the  diameter  of 
from  JT  to  -J-  of  an  inch,  but  which  he  had  succeeded  in  apply- 
ing to  tubes  of  the  diameter  of  the  capillaries.1 

A  red  corpuscle  occasionally  becomes  involved  in  the  still 
layer,  when  it  moves  slowly,  turning  over  and  over,  or  even 
remains  stationary  for  a  time,  until  it  is  taken  up  again  and 
carried  along  with  the  central  current.  A  few  white  corpus- 
cles are  constantly  seen  in  this  layer.  They  move  along 
slowly,  and  apparently  have  a  tendency  to  'adhere  to  the 
walls  of  the  vessel.  This  is  due  to  the  adhesive  character  of 
the  surface  of  the  white  corpuscles  as  compared  with  the  red, 
which  can  easily  be  observed  in  examining  a  drop  of  blood 
between  glass  surfaces,  the  red  corpuscles  moving  about  with 
great  facility,  while  the  white  have  a  tendency  to  adhere. 

Great  differences  exist  in  the  character  of  the  flow  of 
blood  in  the  three  varieties  of  vessels  which  are  under  obser- 
vation. In  the  arterioles,  which  may  be  distinguished  from 
the  capillaries  by  their  size  and  the  presence  of  the  muscular 

1  POISEUILLE,  JRecherches  sur  les  Causes  du  Mouvement  du  Sang  dans  Us  Vais- 
seaux  Capillaires,  p.  144  et  seq. 


PHENOMENA  OF  THE  CAPILLARY    CIRCULATION.  287 

and  fibrous  coats,  the  movement  is  distinctly  remittent,  even 
in  their  most  minute  ramifications.  The  blood  moves  in 
them  with  much  greater  rapidity  than  in  either  the  capil- 
laries or  \7eins.  They  become  smaller  as  they  branch,  and 
carry  the  blood  always  in  the  direction  of  the  capillaries. 
The  veins,  which  are  relatively  larger  than  the  arteries,  carry 
the  blood  more  slowly,  and  in  a  continuous  stream,  from  the 
capillaries  toward  the  heart.  In  both  these  vessels  the  cur- 
rent is  frequently  so  rapid,  that  the  form  of  the  corpuscles 
cannot  be  distinguished.  Only  a  portion  of  the  white  cor- 
puscles occupy  the  still  layer,  the  rest  being  carried  on  in  the 
central  current. 

The  circulation  in  the  true  capillaries  is  sui  generis.  Here 
the  blood  is  distributed  in  every  direction,  in  vessels  of  nearly 
uniform  diameter.  The  vessels  are  generally  so  small  as  to 
admit  but  a  single  row  of  corpuscles,  which  move  almost  like 
beings  endowed  with  volition.  In  a  single  vessel,  a  line  of 
corpuscles  may  be  seen  moving  in  one  direction  at  one  mo- 
ment, and  a  few  moments  after  taking  a  directly  opposite 
course.  Spall anzani,  in  one  of  his  observations,  describes  the 
following  phenomenon.  Two  single  rows  of  corpuscles,  pass- 
ing in  two  capillary  vessels  of  equal  size,  were  directed  to- 
ward a  third  capillary  vessel,  formed  by  the  union  of  the  two 
others,  which  would  itself  admit  but  a  single  corpuscle.  The 
corpuscles  in  one  of  these  vessels  seemed  to  hold  back  until 
those  from  the  other  had  passed  in,  when  they  followed  in  their 
turn.1  When  the  circulation  is  natural,  the  movement  in 
the  capillaries  is  always  quite  slow  compared  with  the  move- 
ment in  the  arterioles,  and  is  continuous.  Here,  at  last,  the 
impulse  of  the  heart  is  lost.  The  corpuscles  do  not  neces 
sarily  circulate  in  all  the  capillaries  which  are  in  the  field  ot 
view.  Certain  vessels  may  not  receive  a  corpuscle  for  some 
time,  but  after  a  while  one  or  two  corpuscles  become  engaged 
in  them,  and  a  current  is  finally  established.  Many  inter- 
esting little  points  are  noticed  in  examining  the  circulation 

1  SPALLANZANI,  Experiences  sur  la  Circulation  Paris,  1808,  p.  177. 


288  CIRCULATION. 

for  a  length  of  time.  A  corpuscle  is  frequently  seen  caught 
at  the  angle  where  a  vessel  divides  into  two,  remaining  fixed 
for  a  time,  distorted  and  bent  by  the  force  of  the  current. 
It  soon  becomes  released,  and,  as  it  enters  the  vessel,  regains 
its  original  form.  In  some  of  the  vessels  of  smallest  size,  the 
corpuscles  are  slightly  deformed  as  they  pass  through. 

The  scene  is  changed  with  every  different  part  which  is 
examined.  In  the  tongue,  in  addition  to  the  arterioles  and 
venules,  with  the  rich  network  of  capillaries,  dark-bordered 
nerve-fibres,  striated  muscular  fibres,  and  pavement  epithe- 
lium can  be  distinguished.  In  the  lungs,  the  view  is  very 
beautiful.  Large,  polygonal  air-cells  are  observed,  bounded 
by  capillary  vessels,  in  which  the  corpuscles  move  with  ex- 
treme rapidity.  It  has  been  observed  that  the  larger  vessels 
are  crowded  to  their  utmost  capacity  with  corpuscles,  leaving 
no  still  layer  next  the  walls,  such  as  is  seen  in  the  circulation 
in  other  situations. 

When  the  circulation  has  been  for  a  long  time  under 
observation,  as  the  animal  becomes  enfeebled,  very  interest- 
ing changes  in  the  character  of  the  flow  of  blood  take  place. 
The  continuous  stream  in  the  smallest  vessels  diminishes 
in  rapidity,  and  after  a  while,  when  the  contractions  of  the 
heart  have  become  infrequent  and  feeble,  the  blood  is  nearly 
arrested,  even  in  the  smallest  capillaries,  during  the  intervals 
of  the  heart's  action,  and  the  current  becomes  remittent. 
As  the  central  organ  becomes  more  and  more  enfeebled,  the 
circulation  becomes  intermittent ;  the  blood  receiving  an 
impulse  from  each  contraction,  but  remaining  stationary 
during  the  intervals.  At  this  time,  the  corpuscles  cease  to 
occupy  exclusively  the  central  portion  of  the  vessels,  and  the 
clear  layer  of  plasma  next  their  walls,  which  was  ob- 
served in  the  normal  circulation,  is  no  longer  apparent. 
Following  this,  there  is  actual  oscillation  in  the  capillaries. 
At  each  contraction  of  the  heart,  the  blood  is  forced  onwards 
a  little  distance,  but  almost  immediately  returns  to  about  its 
former  position.  This  phenomenon  has  long  been  observed, 


RAPIDITY   OF  THE   CAPILLARY   CIRCULATION.  289 

and  is  explained  in  the  following  way :  As  the  heart  has 
become  enfeebled,  the  contractions  are  so  infrequent  and  in- 
effectual, that  during  their  intervals  the  constant  flow  in  the 
capillaries  is  entirely  arrested ;  for  the  arterial  pressure,  which 
is  its  immediate  cause,  and  which  is  maintained  by  the  suc- 
cessive charges  of  blood  sent  into  the  arteries  at  each  ventric- 
ular systole,  is  lost.  But  as  the  blood  is  contained  in  a  con- 
nected system  of  closed  tubes,  the  feeble  impulse  of  the  heart 
is  propagated  through  the  vessels  and  produces  a  slight  im- 
pulse, even  in  the  smallest  capillaries,  which  dilates  them 
and  forces  the  fluid  a  little  distance.  As  soon,  however,  as 
the  heart  ceases  to  contract,  the  current  is  arrested,  and  the 
blood,  meeting  with  a  certain  amount  of  obstniction  from  the 
fluid  in  the  small  veins,  which  are  still  further  removed  from 
the  heart,  is  made  to  return  to  its  former  position. 

This  phenomenon  continues  for  a  short  time  only,  for  the 
heart  soon  loses  its  contractility,  and  the  circulation  in  all  the 
vessels  is  permanently  arrested. 

Rapidity  of  the  Capillary  Circulation. — The  circulation 
in  the  capillaries  of  a  part  is  subject  to  such  great  variations, 
and  the  differences  in  different  situations  are  so  considerable, 
that  it  is  impossible  to  give  any  definite  rate  which  will 
represent  the  rapidity  of  the  capillary  circulation.  It  is  for 
this  reason  that  it  has  been  found  impracticable  to  estimate 
the  capacity  of  the  capillary,  as  compared  with  the  arterial, 
system.  The  rapidity  of  the  flow  of  blood  is  by  no  means 
as  great  as  it  appears  in  microscopic  examinations;  being, 
of  course,  exaggerated  in  proportion  to  the  magnifying  power 
employed.  It  is,  nevertheless,  to  microscopic  investigations 
that  we  are  indebted  for  the  scanty  information  we  possess 
on  this  subject.  The  estimates  which  have  been  made  by 
various  observers  refer  generally  to  cold-blooded  animals,  and 
have  been  arrived  at  by  simply  calculating  the  time  occupied 
by  a  blood-corpuscle  in  passing  over  a  certain  distance.  Hales, 
who  was  the  first  to  investigate  this  question,  estimated  that 
19 


290  CIRCULATION. 

in  the  frog  a  corpuscle  moved  at  the  rate  of  an  inch  in  ninety 
seconds.1  The  estimates  of  Weber  and  Yalentin  are  con- 
'  siderably  higher,  being  about  -fa  °f  an  incn  Per  second. 
Yolkmann  calculated  the  rapidity  in  the  mesentery  of  the 
dog,  which  would  approximate  more  nearly  to  the  human 
subject,  and  found  it  to  be  aftout  -fa  of  an  inch  per  second.3 
Yierordt  made  a  number  of  curious  observations  upon  him- 
self, by  which  he  professed  to  be  able  to  estimate  the  rapidity 
of  the  circulation  in  the  little  vessels  of  the  eye.  He  states 
that  when  the  eye  is  fatigued,  and  sometimes  when  the  ner- 
vous system  is  disordered,  compression  of  the  globe  in  a  cer- 
tain way  will  enable  one  to  see  a  current  like  that  in  a  capil- 
lary plexus.  This  he  believes  to  be  the  capillary  circulation, 
and  by  certain  calculations  he  formed  an  estimate  of  its  rapid- 
ity, putting  it  at  from  -fa  to  -fa  of  an  inch.  The  latter  figure 
accords  pretty  nearly  with  the  observations  of  Yolkmann 
upon  the  dog.3  How  far  these  observations  are  to  be  relied 
upon  it  is  impossible  to  say.  Certainly  no  great  importance 
would  be  attached  to  them  if  they  did  not,  in  their  results, 
approximate  to  the  estimates  of  Yolkmann,  which  probably 
represent,  more  nearly  than  any,  the  rapidity  in  the  capil- 
laries of  the  human  subject. 

After  what  has  been  said  of  the  variations  in  the  capillary 
circulation,  it  is  evident  that  the  foregoing  estimates  are  by 
no  means  to  be  considered  exact. 

delations  of  the  Capillary  Circulation  to  Respiration. — - 
In  treating  of  the  influence  of  respiration  upon  the  action  of 
the  heart,  the  arterial  pressure,  pulse,  etc.,  it  has  already 
been  stated  that  non-aerated  blood  cannot  circulate  freely  in 
the  capillaries.  Yarious  ideas  with  regard  to  the  effects  of 
asphyxia  upon  the  circulation  have  been  advanced,  which 
will  be  again  discussed  in  connection  with  respiration.  The 

1  Statical  Essays,  containing  Hcemastaticks,  London,  1733,  p.  68. 

a  MILNE-EDWARDS,  Lemons  sur  la  Physiologic,  Paris,  1859,  tome  iv.,  p.  286. 

'Ibid. 


RELATIONS   TO  KESPIKATION.  291 

fact  is  evident,  that  arrest  of  respiration  produces  arrest  of 
circulation.  This  is  ordinarily  attributed  to  an  impediment 
to  the  passage  of  blood  through  the  lungs,  when  they  no 
longer  contain  the  proper  quantity  of  oxygen.  This  view  is 
entirely  theoretical,  and  has  been  disproved  by  experiments 
dating  more  than  half  a  century  ago.  In  1789,  Goodwyn 
advanced  the  theory  that,  in  asphyxia,  the  blood  passes 
through  the  lungs,  but  is  incapable  of  exciting  contractions 
in  the  left  ventricle.1  Bichat,  in  his  celebrated  essay  "  Sur 
la  Vie  et  la  Mort"  1805,  proved  by  experiment  that  black 
blood  passes  through  the  lungs  in  asphyxia,  and  is  found  in 
the  arteries.  His  theory  was  that  non-aerated  blood,  circu- 
lating in  the  capillaries  of  the  nervous  centres,  arrests  their 
function,  thus  acting  indirectly  upon  the  circulation ;  and 
that  finally  the  heart  itself  is  paralyzed  by  the  circulation  of 
black  blood  in  its  substance. 

Dr.  John  Keid,  in  an  article  "  On  the  Cessation  of  the 
Yital  Actions  in  Asphyxia," a  describes  an  experiment  in  which 
a  hemodynamometer  applied  to  the  femoral  artery  of  a  dog 
indicated  increase  in  the  arterial  pressure  during  the  first 
moments  of  asphyxia,  followed  finally  by  a  depression  in  the 
mercury.  He  found  a  corresponding  diminution  in  the 
pressure  in  the  vein  of  the  opposite  side.  "  This  was  so  un- 
looked  for — at  first  sight  so  inexplicable,  and  so  much  at 
variance  with  my  preconceived  notions  on  the  subject,"  says 
the  author,  "that  I  was  strongly  inclined  to  believe  there 
must  be  some  source  of  fallacy ;  but  after  repeating  the  ex- 
periment more  than  twenty  times,  and  invariably  with  the 
same  results,  I  was  at  last  compelled  to  admit  its  accuracy." 
This  he  surmises  is  due  to  "  an  impediment  to  the  passage  of 
the  venous  blood  through  the  capillaries  of  the  systemic  cir- 
culation." In  his  conclusions  at  the  end  of  the  article,  how- 

1  P.  BERARD,  Cours  de  Physiologic  fait  d  la  Faculte  de  Medecine  de  Paris, 
1851,  tome  iii.,  p.  444. 

a  JOHN  REID,  M.  D.,  Physiological,  Anatomical,  and  Pathological  Researches, 
Edinburgh,  1848,  p.  26.  (Article  extracted  from  the  Edinburgh  Medical  and 
Surgical  Journal,  April,  1841.) 


CIRCULATION. 

ever,  he  takes  no  account  of  the  results  of  this  experiment, 
which  point  conclusively  to  arrest  of  blood  in  the  capillary 
system,  and  the  conclusions  with  regard  to  the  effect  of  as- 
phyxia upon  the  circulation  are  substantially  those  of  Bichat. 

The  immediate  effects  of  asphyxia  upon  the  circulation 
are  referable  to  the  general  capillary  system.  This  fact  was 
demonstrated  by  experiments  on  the  frog  published  in  1857.  * 
In  these  experiments,  the  medulla  oblongata  was  broken 
up,  and  the  web  of  the  foot  submitted  to  microscopic  exam- 
ination. This  operation  does  not  interfere  with  the  circula- 
tion, which  may  be  observed  for  hours  without  difficulty. 
The  cutaneous  surface  was  then  coated  with  collodion,  care 
only  being  taken  to  avoid  the  web  under  observation.  The 
effect  on  the  circulation  was  immediate.  It  instantly  be- 
came less  rapid,  until,  at  the  expiration  of  twenty  minutes, 
it  had  entirely  ceased.  The  entire  coating  of  collodion  was 
then  instantly  peeled  off.  Quite  a  rapid  circulation  imme- 
diately commenced,  but  it  soon  began  to  decline,  and  in 
twenty  minutes  had  almost  ceased.  In  another  observation, 
the  coating  of  collodion  was  applied  without  destroying  the 
medulla.  The  circulation  was  affected  in  the  same  manner 
as  before,  and  ceased  in  twenty-five  minutes. 

These  experiments,  taken  in  connection  with  observations 
on  the  influence  of  asphyxia  upon  the  arterial  pressure,  con- 
clusively show  that  non-aerated  blood  cannot  circulate  freely 
in  the  systemic  capillaries.2  Yenous  blood,  however,  can  be 
forced  through  them  with  a  syringe,  and  even  in  asphyxia  it 
filters  slowly  through,  and  if  air  be  admitted  to  the  lungs 
before  the  heart  has  lost  its  contractility,  the  circulation's 
restored. 

Eb  differences  in  the  capillary  circulation  have  been  no- 

1  See  article  by  the  author,  entitled  "Phenomena  of  the  Capillary  Circula- 
tion," American  Journal  of  the  Medical  Sciences,  July,  1857. 

2  In  these  experiments,  ether  had  previously  been  freely  applied  to  the  surface 
to  render  it  certain  that  the  effects  on  the  circulation  were  not  the  result  of  this 
ingredient  of  the  collodion. 


CAUSES   OF  THE   CAPILLARY   CIRCULATION.  293 

ticed  accompanying  the  ordinary  acts  of  inspiration   and 
expiration. 

Causes  of  the  Capillary  Circulation. — The  contractions 
of  the  left  ventricle  are  evidently  capable  of  giving  an  im- 
pulse to  the  blood  in  the  smallest  arterioles,  for  a  marked  ac- 
celeration of  the  current  accompanying  each  systole  can  be 
distinguished  in  all  but  the  true  capillaries.  It  has  also  been 
shown  by  experiments  after  death,  that  blood  can  be  forced 
through  the  capillary  system  and  returned  by  the  veins  by  a 
force  less  than  that  exerted  by  the  heart.  This,  however, 
cannot  rigidly  be  applied  to  the  natural  circulation,  as  the 
smallest  arteries  are  endowed  during  life  with  contractility, 
which  is.  capable  of  modifying  the  blood  current.1  Dr. 
Sharpey  adapted  a  syringe,  with  a  hemodynamometer  at- 
tached, to  the  aorta  of  a  dog  just  killed,  and  found  that  fresh 
defibrinated  blood  could  be  made  to  pass  through  the  double 
capillary  systems  of  the  intestines  and  liver,  by  a  pressure  of 
three  and  a  half  inches  of  mercury.  It  spurted  out  at  the 
vein  in  a  full  jet  under  a  pressure  of  five  inches.  In  this  ob- 
servation, the  aorta  was  tied  just  above  the  renal  arteries. 
The  same  pressure,  the  ligature  being  removed,  forced  the 
blood  through  the  capillaries  of  the  inferior  extremities.2 
This  is  much  less  than  the  arterial  pressure,  which  is  equal 
to  from  five  and  a  half  to  six  inches  of  mercury. 

It  is  thus  seen  that  the  pressure  in  the  arteries  which 
forces  the  blood  toward  the  capillaries  is  competent,  unless 
opposed  by  excessive  contraction  of  the  arterioles,  not  only  to 
cause  the  blood  to  circulate  in  these  vessels,  but  to  return  it  to 
the  heart  by  the  veins.  This  fact  is  so  evident,  that  it  is  un- 

1  As  showing  the  difference  between  the  vessels  immediately  after  death,  and 
after  they  have  lost  all  their  vital  properties,  we  may  refer  to  an  observation  of 
Berard  (op.  cit.,  p.  776),  in  which  he  found  it  impossible  to  inject,  with  a  solidifi- 
able  fluid,  parts  of  the  body  immediately  after  amputation.    Water  passed  with 
facility,  but  alcohol  or  vinegar  could  not  be  forced  through. 

2  TODD  and  BOWMAN,  The  Physiological  Anatomy  and  Physiology  of  Man, 
Philadelphia,  1857,  p.  678. 


294:  CIRCULATION. 

necessary  to  discuss  the  views  of  Bichat,  and  some  others, 
who  supposed  that  the  action  of  the  heart  had  no  effect  upon 
the  capillary  circulation.  It  must  be  admitted  that  this  is  its 
prime  cause ;  and  the  only  questions  to  be  considered  are, 
first,  whether  there  be  any  reason  why  the  force  of  the  heart 
should  not  operate  on  the  blood  in  the  capillaries,  and 
second,  whether  there  be  any  force  in  these  vessels  which 
is  superadded  to  the  action  of  the  heart. 

The  first  of  these  questions  is  answered  by  microscopic 
observations  on  the  circulation.  A  distinct  impulse,  follow- 
ing each  ventricular  systole,  is  observed  in  the  smallest  ar- 
teries. The  blood  flows  from  them  directly  and  freely  into 
the  capillaries ;  and  there  is  not  the  slightest  ground  for  the 
supposition  that  the  force  is  not  propagated  to  this  system  of 
vessels. 

Various  writers  have  supposed  the  existence  of  a  "  capil- 
lary power,"  which  they  have  regarded  as  of  greater  or  less 
importance  in  producing  the  capillary  circulation.  The 
views  of  some  are  purely  theoretical,  but  others  base  their 
opinion  on  microscopic  observations.  These  views  do  not 
demand  an  extended  discussion.  There  is  a  force  in  opera- 
tion, the  action  of  the  heart,  which  is  capable  of  producing 
the  capillary  circulation ;  and  there  is  nothing  in  the  phenom- 
ena of  the  circulation  in  these  vessels,  which  is  inconsistent 
with  its*  full  operation.  Under  these  circumstances,  it  is 
unphilosophical  to  invoke  the  aid  of  the  currents  produced 
in  capillary  tubes  in  which  liquids  of  different  characters  are 
brought  ID  contact,  or  a  "  capillary  power  "  dependent  upon 
a  vital  nutritive  attraction  between  the  tissues  and  the  blood, 
unless  we  do  it  on  the  basis  of  phenomena  observed  in  the 
capillaries  when  the  action  of  the  heart  is  suppressed. 
When  the  heart  ceases  its  action,  movements  in  the 
capillaries  are  sometimes  due  to  the  contractions  of  the  ar- 
teries, a  property  which  has  already  been  fully  considered. 
Movements  which  have  been  observed  in  membranes  de- 
tached from  the  body  are  due  to  the  mere  emptying  of  the 


CAUSES   OF  THE   CAPILLARY   CIRCULATION.  295 

divided  vessels  or  simple  gravitation.  It  must  be  remem- 
bered that  in  microscopic  examinations,  the  movements  which 
are  observed  are  immensely  exaggerated  by  the  magnifying 
power,  and  we  receive,  at  first  sight,  an  erroneous  idea  of 
their  rapidity.  The  movements  of  the  blood  in  detached 
membranes,  due  merely  to  gravity,  have  been  so  satisfactorily 
explained  by  the  experiments  of  Poiseuille,  that  it  is  deemed 
unnecessary  to  refer  to  the  observations  of  those  who  have 
attributed  this  phenomenon  to  other  causes.1 

Dr.  Dowler,  of  New  Orleans,  made  some  experiments  on 
the  circulation  in  patients  dead  with  yellow  fever,  in  which 
he  found  that  the  blood  would  flow  in  a  tolerably  full  stream 
from  a  punctured  vein  a  few  minutes  after  death.  This  he 
attributes  to  an  independent  action  of  the  capillaries,  which 
continues  for  a  time  after  the  action  of  the  heart  has 
ceased.3  These  observations  are  met  by  the  following  experi- 
ment performed  years  before  by  Magendie.3  A  ligature  was 
passed  around  the  thigh  of  a  dog,  leaving  only  the  crural 
artery  and  vein.  A  ligature  was  then  applied  to  the  vein, 
and  a  small  opening  made  below  it  in  the  vessel,  from  which 
the  blood  escaped  in  a  jet.  On  compressing  the  artery,  the 
flow  of  blood  was  not  immediately  arrested  in  the  vein,  but 
continued  to  gradually  diminish  in  force  until  it  stopped  after 
a  few  moments.  On  examining  the  artery  below  the  point 
of  compression,  it  was  found  contracted,  and  completely 
emptied  of  blood,  while  the  vein  was  full  below  the  punc- 
ture. The  pressure  being  removed  from  the  artery,  the  blood 
commenced  to  flow  from  the  vein,  and  a  jet  was  soon  estab- 
lished as  before.  When  the  artery  was  slightly  compressed, 
so  as  to  allow  the  passage  of  a  small  quantity  of  blood,  not 
enough  to  distend  the  vessel,  the  blood  flowed  from  the  vein, 
but  no  longer  in  a  jet.  This  experiment  shows  that  when 

1  POISEUILLE,  Recherches  sur  les  Causes  du  Mouvement  du  Sang  dans  les  Vats- 
seaux  Capillaires,  1835,  p.  127. 

3  DUNGLISON,  Human  Physiology,  Philadelphia,  1851,  vol.  i.,  p.  420 

3  MAGENDIE,  Precis  filementaire  de  Physiologic,  Paris,  1836,  tome  ii.,  p.  390. 


296  CIRCULATION. 

an  artery  supplying  a  part  with  blood  is  removed  from  the 
influence  of  the  heart,  the  vessel  will  contract  and  force  its 
contents  into  the  vein.  This  affords  the  most  rational  expla- 
nation of  the  phenomena  observed  by  Dr.  Dowler.  When 
the  blood  is  allowed  to  enter  slowly,  so  as  not  to  distend  the 
vessel,  though  it  be  supplied  *to  the  capillary  system,  it  does 
not  there  undergo  any  propelling  influence,  competent,  at  any 
time,  to  increase  the  rapidity  of  the  flow  from  the  vein. 

Physiologists  who,  like  Bichat,1  have  been  unable  to 
explain  the  local  variations  in  the  capillary  circulation  with- 
out the  intervention  of  a  force  resident  in  these  vessels  or  the 
surrounding  tissues,  have  not  appreciated  the  action  of  the 
arterioles.  These  little  vessels  are  endowed  to  an  eminent 
degree  with  contractility  and,  by  the  contractions  and  re- 
laxations of  their  muscular  walls,  regulate  the  supply  of  blood 
to  the  capillaries  of  individual  parts.  Their  action  is  com- 
petent to  produce  all  the  variations  which  are  observed  in  the 
capillary  circulation. 

It  is  evident,  then,  that  the  arterial  pressure,  which  is 
itself  derived  from  the  action  of  the  heart,  is  competent  to 
produce  the  circulation  of  the  blood,  as  we  observe  it,  with 
all  its  variations,  in  the  capillary  vessels ;  that  there  is  no 
evidence  of  the  intervention  of  any  other  force,  but,  on  the 
contrary,  microscopic  observations  and  experiments  on  the 
arteries  and  veins,  thus  far,  show  that  there  is  no  other  force 
in  operation.2 

1  Loc.  cit. 

2  It  has  been  asserted  that  there  is  a  circulation  of  the  blood  in  the  area  vas- 
culosa,  the  first  blood-vessels  that  are  developed,  before  the  heart  is  formed ;  but 
there  are  no  definite  and  reliable  observations  which  show  that  there  is  any  regular 
movement  of  the  blood,  which  can  be  likened  to  the  circulation. as  it  is  observed 
after  the  development  of  the  heart,  anterior  to  the  appearance  of  a  contractile 
central  organ.    Another  example  of  what  is  supposed  to  be  circulation  without 
the  intervention  of  the  heart  is  in  cases  of  acardiac  foetuses.     Monsters  without  a 
heart,  which  have  undergone  considerable  development  and  which  present  systems 
of  arteries,  capillaries,  and  veins,  have  been  described.     All  of  these,  however, 
are  accompanied  by  a  twin,  in  which  the  development  of  the  circulatory  system  is 


INFLUENCE  OF  TEMPERATURE.  297 

Influence  of  Temperature  on  the  Capillary  Circulation. — 
Within  moderate  limits,  a  low  temperature,  induced  by  local 
applications,  has  been  found  to  diminish  the  quantity  of  blood 
sent  to  the  capillaries,  and  retard  the  circulation;  while  a 
high  temperature  increases  the  supply  of  blood  and  acceler- 
ates its  current.  The  mechanism  of  this  is  beautifully  shown 
by  the  experiments  of  Poiseuille.  This  observer  found  that 
when  a  piece  of  ice  was  applied  to  the  web  of  a  frog's  foot, 
the  mesentery  of  a  small  warm-blooded  animal,  or  any  part 
in  which  the  capillary  circulation  can  be  observed,  the  quan- 
tity of  corpuscles  circulating  in  the  arterioles  became  very 
much  diminished,  "  those  which  carried  two  or  three  rows 
of  corpuscles  giving  passage  to  but  a  single  row."  The  cir- 
culation in  the  capillaries  first  became  slower,  and  then  en- 
tirely ceased  in  parts.  On  removing  the  ice,  in  a  very  few 
minutes  the  circulation  regained  its  former  characters. 

If,  on  the  other  hand,  the  part  be  covered  with  water  at 
1040,  the  rapidity  of  the  current  in  the  capillaries  is  so  much 

perfect.  The  most  remarkable  case  of  this  kind  is  one  reported  by  Dr.  Houston 
in  the  Dublin  Journal  of  Medical  Science  (1836,  vol.  x.,  p.  204).  In  this  case 
there  was  a  perfect  twin,  but  two  distinct  cords  and  sets  of  membranes.  Dr. 
Houston  supposed  that  the  circulation  in  this  monster  was  carried  on  by  "  capil- 
lary power "  alone.  In  these  cases,  as  has  been  shown  by  Astley  Cooper  and 
Lallemand  (Edinburgh  Medical  and  Surgical  Journal,  1844,  vol.  Ixii.,  p.  156  et 
seq.\  there  is  a  free  anastomosis  of  the  vessels  of  the  two  foetuses  in  the  placenta. 
Some  have  supposed,  from  the  fact  that  the  veins  of  the  monster  are  not  provided 
with  valves,  that  in  it  the  circulation  is  from  the  veins  to  the  arteries,  or  is  inverted. 
It  is  not  exactly  clear  how  the  circulation  is  carried  on  in  an  acardiac  foetus.  Un- 
doubtedly the  heart  of  one  child  may  influence  the  circulation  in  the  umbilical 
vessels  of  the  other,  in  cases  of  twins ;  for  Lallemand  has  observed  (loc.  cit.\  after 
the  birth  of  one  child,  the  cord  having  been  divided,  a  regular  pulsatile  flow  from 
the  placental  extremity  of  the  cord,  as  from  a  divided  artery ;  but  we  find  on 
careful  examination  of  the  case  reported  by  Dr.  Houston,  and  an  article  on  the 
case  by  Dr.  G.  Calvert  Holland  (Edinburgh  Med.  and  Surg.  Journal,  loc.  cit.\  no 
sufficient  evidence  that  the  circulation  was  carried  on  by  any  "  capillary  power." 
Not  being  able  to  regard  as  facts  these  grounds,  on  which  some  have  based  their 
belief  in  the  existence  of  a  force  in  the  circulation  which  is  independent  of  the 
heart's  action,  we  have  abstained  from  their  discussion  in  treating  of  the  causes 
of  the  capillary  circulation. 


298  CIRCULATION. 

increased,  that  we  can  hardly  distinguish  the  form  of  the 
corpuscles.1 

Influence  of  Direct  Irritation  upon  the  Capillary  Circu- 
lation.— Experimental  researches  on  the  effects  of  direct  irri- 
tation of  the  capillaries,  in  parts  where  the  circulation  can 
be  observed  microscopically,  have  been  quite  numerous  since 
Thompson  studied  the  effects  of  saline  solutions  on  the  web 
of  the  frog's  foot  in  1 813.'  The  most  noticeable  papers  on 
this  subject  are  those  of  Dr.  Wilson  Philip 3  and  Mr.  Wharton 
Jones.4  The  latter  paper,  which  received  the  Astley  Cooper 
prize  for  1850,  is  based  on  very  extended  and  carefully 
conducted  observations,  in  which  the  author,  by  means  of 
various  irritants,  succeeded  in  producing  very  curious  and 
interesting  phenomena,  which  he  regarded  as  inflammatory. 
It  is  not  our  object  to  discuss  the  nature  of  inflammation,  or 
to  treat  of  the  changes  in  the  character  of  the  capillary  circu- 
lation which  are  supposed  to  attend  this  condition,  as  this 
subject  is  eminently  pathological ;  but  it  must  be  remember- 
ed, in  considering  the  effects  of  direct  irritation  on  the  capil- 
lary circulation,  that  the  phenomena  thus  observed  in  cold- 
blooded animals  cannot  be  taken  as  absolutely  representing 
the  characters  of  inflammation  in  the  human  subject.  When 
an  irritation  is  applied  to  a  transparent  part,  the  phenomena 
observed  may  be  due  to  many  causes,  as  the  direct  effects 
upon  the  contractile  elements  of  the  blood-vessels,  the  reflex 
action  through  the  nervous  system,  and  the  direct  influence 
of  the  application  upon  the  constitution  of  the  blood.  Saline 
or  other  fluids  are  competent  to  modify,  to  a  very  consider- 
able extent,  the  composition  of  the  blood,  separated  from  it 
only  by  the  thin,  permeable  -walls  of  the  vessels ;  and  the 

1  POISEUILLE,  op.  c'd.,  p.  158  ei  seq. 

2  THOMPSON,  Lectures  on  Inflammation,  Edinburgh,  1818. 
8  Medico-  Chirurgical  Transactions,  1823,  vol.  xii. 

4  Guy's  Hospital  Reports,  vol.  vii.,  1851,  On  the  State  of  the  Blood  and  tJie 
Blood-vessels  in  Inflammation,  ascertained  by  Experiments,  Injections,  and  Obser- 
vations by  the  Microscope,  by  T.  WHARTON  JONES,  F.  R.  & 


INFLUENCE   OF  IRRITATION.  299 

phenomena  which  follow  their  application  are  necessarily 
very  complex.  The  process  of  inflammation  is  by  no  means 
completely  understood,  but  it  is  pretty  generally  acknowl- 
edged to  be  a  modification  of  nutrition,  in  a  way  that  we  are 
as  yet  ignorant  of.  We  are  hardly  prepared  to  admit  that 
this  modification,  whatever  it  may  be,  can  be  induced  under 
our  very  eyes,  simply  by  the  application  of  irritants.  With 
these  views,  microscopic  researches  on  the  "  state  of  the  blood 
and  blood-vessels  in  inflammation "  do  not  assume  the  im- 
portance which  is  attributed  to  them  by  many  authors. 

Keeping  this  in  mind,  we  may  state  the  following  as  a 
summary  of  the  phenomena  which  have  been  observed  in 
the  capillary  circulation,  as  the  result  of  irritation  applied  to 
transparent  parts : 

The  application  of  the  irritant  is  immediately  followed  by 
constriction  of  the  arterioles,  and  diminution  in  the  rapidity 
of  the  current  in  them  as  well  as  in  the  capillaries. 

This  constriction  of  the  vessels  is  but  momentary,  if  a 
powerful  irritant,  like  a  very  strong  solution  of  salt,  be  used. 
It  is  followed  by  a  dilatation  of  the  vessels,  and  an  increase  in 
the  rapidity  of  the  circulation. 

Soon  after  the  vessels  have  become  dilated,  the  rapidity 
of  the  circulation  is  progressively  diminished,  until  oscillation 
of  the  blood  in  the  vessels  takes  place,  which  occurs  when 
the  circulation  is  about  to  cease.  This  oscillation  finally 
gives  place  to  complete  stagnation.  The  vessels  become 
crowded  with  blood,  so  that  the  transparent  layer  next 
their  walls  is  no  longer  observed.  In  this  condition,  it  has 
been  often  noticed  that  the  proportion  of  colorless  corpuscles 
is  increased. 

Following  the  contraction  and  subsequent  dilatation  of  the 
vessels,  there  is  stasis,  and  engorgement  of  the  parts  which 
have  been  exposed  to  irritation.  If  the  irritation  be  discon- 
tinued, this  condition  is  gradually  relieved,  and  the  blood  re- 
sumes its  normal  current. 

In  inflammation,  as  it  is  observed  in  the  conjunctiva  and 


300  CIRCULATION. 

other  vascular  parts,  there  is  unquestionably  congestion  of  the 
vessels ;  but  there  is  no  positive  evidence  of  stagnation  of 
blood  in  the  parts  as  a  constant  occurrence.  The  circula- 
tion seems,  indeed,  to  be  more  active  than  in  health.  With 
regard  to  the  microscopic  phenomena  just  mentioned,  the 
contraction  of  the  arterioles  is'simply  the  effect  of  a  stimulus 
upon  their  muscular  coats ;  and  dilatation  takes  place  prob- 
ably in  consequence  of  the  excessive  contraction,  for  it  has 
been  shown  that  this  condition  of  the  muscular  fibres  is  pretty 
constantly  followed  by  unusual  relaxation.  It  has  never  yet 
been  determined  how  far  the  stasis  of  the  blood  is  due  to  an 
osmotic  action  of  solutions  employed  in  observations  of  this 
kind. 


CHAPTEK  VIII. 

CIRCULATION   OF   THE    BLOOD   IN   THE   VEINS. 

Physiological  anatomy  of  the  veins — Strength  of  the  coats  of  the  veins — Valves 
of  the  veins — Course  of  the  blood  in  the  veins — Pressure  of  blood  in  the 
veins — Rapidity  of  the  venous  circulation — Causes  of  the  venous  circulation — 
Influence  of  muscular  contraction — Air  in  the  veins — Function  of  the  valves — 
Venous  anastomoses — Conditions  which  impede  the  venous  circulation — Re- 
gurgitant  venous  pulse. 

Physiological  Anatomy  of  the  Veins. — The  blood,  dis- 
tributed to  the  capillaries  of  all  the  tissues  and  organs  by  the 
arteries,  is  collected  from  these  parts  in  the  veins  and  carried 
back  to  the  heart.  In  studying  the  anatomy  of  the  capillary 
system,  or  in  observing  the  passage  of  the  blood  from  the 
capillaries  to  larger  vessels,  in  parts  of  the  living  organism 
which  can  be  submitted  to  microscopic  examination,  it  is 
seen  that  the  capillaries,  vessels  of  nearly  uniform  diameter 
and  anastomosing  in  every  direction,  give  origin,  so  to  speak, 
to  a  system  of  vessels,  which,  by  union  with  others  as  we  fol- 
low their  course,  become  larger  and  larger,  and  carry  the 
blood  away  in  a  uniform  current.  These  are  called  the 
venules,  or  venous  radicles.  They  are  the  peripheral  radicles 
of  the  numerous  vessels  which  transport  the  blood,  after  it 
has  served  the  purposes  of  nutrition  or  secretion,  to  the  cen- 
tral organ. 

The  venous  system  may  be  considered,  in  general  terms, 
as  divided  into  two  sets  of  vessels  :  one,  which  is  deep,  and 


CIRCULATION. 

situated  in  proximity  to  the  arteries ;  and  the  other,  which 
is  superficial,  and  receives  for  the  most  part  the  blood  from 
the  cutaneous  surface.  The  entire  capacity  of  these  vessels, 
as  compared  with  the  arteries,  is  very  great.  As  a  general 
rule,  each  vein  when  fully  distended  is  larger  than  its  adja- 
cent artery.  Many  arteries  are  accompanied  by  two  veins, 
as  the  arteries  of  the  extremities;  while  certain  of  them,  like 
the  brachial  or  spermatic,  have  more  than  two.  Added  to 
these  is  the  superficial  system  of  veins  which  have  no  corre- 
sponding arteries.  It  is  true  that  some  arteries  have  no  cor- 
responding veins,  but  examples  of  this  kind  are  not  sufficient- 
ly numerous  to  diminish,  in  any  marked  degree,  the  great 
preponderance  of  the  veins,  both  in  number  and  volume.  It 
is  impossible  to  give  an  accurate  estimate  of  the  extreme  ca- 
pacity of  the  veins  as  compared  with  the  arteries ;  but  from 
the  best  information  we  have,  it  is  several  times  greater. 
Borelli  estimated  that  the  capacity  of  the  veins  was,  to  the 
capacity  of  the  arteries,  as  4  to  1 ;  and  Haller,  as  2J  to  1. 
The  proportion  is  very  variable  in  different  parts  of  the  body. 
In  some  situations  the  capacity  of  the  veins  and  arteries  is 
about  equal ;  while  in  others,  as  in  the  pia  mater,  according 
to  the  researches  of  Hirschfeld,  the  veins  will  contain  six 
times  as  much  as  the  arteries.1 

In  attempting  to  compare  the  quantity  of  blood  normally 
circulating  in  the  veins,  with  that  contained  in  the  arteries, 
such  variations  in  the  venous  system  at  different  times  and 
in  different  parts,  both  in  the  quantity  of  blood,  rapidity  of 
circulation,  pressure,  etc.,  are  found,  that  a  definite  estimate 
is  impossible.  It  would  be  unphilosophical  to  attempt  an 
approximate  comparison,  as  the  variations  in  the  venous  cir- 
culation constitute  one  of  its  greatest  and  most  important 
physiological  peculiarities,  which  must  be  fully  appreciated 
in  order  to  form  a  just  idea  of  the  function  of  the  veins. 

1  BERARD,  Cours  de  Physiologic,  Paris,  1855,  tome  iv.,  p.  Y.  The  circulation 
in  the  erectile  tissues  will  be  separately  considered,  and  no  account  is  now  taken 
of  the  relative  capacity  of  veins  and  arteries  in  them. 


PHYSIOLOGICAL   ANATOMY   OF   THE  VEINS.  303 

The  arteries  are  always  full,  and  their  tension  is  subject  to 
comparatively  slight  variations.  Following  the  blood  into 
the  capillaries,  there  are  the  immense  variations  in  the  circu- 
lation with  varying  physiological  conditions  of  the  parts, 
which  we  have  already  noted.  As  should  naturally  be  ex- 
pected, the  condition  of  the  veins  varies  with  the  changes  in 
the  capillaries,  from  which  the  blood  is  taken.  In  addition 
to  this,  there  are  independent  variations,  as  in  the  erectile 
tissues,  in  the  veins  of  the  alimentary  canal  during  absorp- 
tion, in  veins  subject  to  pressure,  etc. 

Following  the  veins  in  their  course,  it  is  observed  that 
anastomoses  with  each  other  form  the  rule  and  not  the 
exception,  as  in  the  arteries.  There  are  always  a  number  of 
channels  by  which  the  blood  may  be  returned  from  a  part ; 
and  if  one  vessel  be  obstructed  from  any  cause,  the  current 
is  simply  diverted  into  another.  The  veins  do  not  present  a 
true  anastomosing  plexus,  such  as  exists  in  the  capillary  sys- 
tem, but  simply  an  arrangement  by  which  the  blood  can 
easily  find  its  way  back  to  the  heart,  and  by  which  the  ves- 
sels may  accommodate  themselves  to  the  immense  variations 
in  the  quantity  of  fluid  contents  to  which  they  are  liable. 
This,  with  the  peculiar  valvular  arrangement  in  all  but  the 
veins  of  the  cavities,  provides  against  obstruction  to  the  flow 
of  blood  through,  as  well  as  from,  the  capillaries,  in  which 
it  seems  essential  to  the  proper  nutrition  and  function  of 
parts,  that  the  quantity  and  course  of  the  blood  should  be 
regulated  exclusively  through  the  arterial  system.  Special 
allusion  to  the  different  venous  anastomoses  belongs  to  de- 
scriptive anatomy.  Physiologically,  the  communication  be- 
tween the  different  veins  is  such  that  the  blood  can  always 
find  a  way  to  the  heart,  and  once  fairly  out  of  the  capillaries, 
it  cannot  react  and  influence  the  circulation  of  fresh  blood  in 
the  tissues. 

Collected  in  this  way  from  all  parts  of  the  body,  the  blood 
is  returned  to  the  right  auricle,  from  the  head  and  upper 
extremities,  by  the  superior  vena  cava,  from  the  trunk  and 


304:  CIRCULATION. 

lower  extremities,  by  the  inferior  yena  cava,  and  from  the 
substance  of  the  heart,  by  the  coronary  veins. 

Structure  and  Properties  of  the  Veins. — The  structure  of 
the  veins  is  somewhat  more  complex  and  difficult  of  study  than 
that  of  the  arteries.  Their  walls,  which  are  always  much 
thinner  than  the  walls  of  the  arteries,  may  be  divided  into 
quite  a  number  of  layers ;  but  for  convenience  of  physiologi- 
cal description,  we  shall  regard  them  as  presenting  three  dis- 
tinct coats.  These  have  properties  which  are  tolerably  distinc- 
tive, though  not  as  much  so  as  the  three  coats  of  the  arteries. 

The  internal  coat  is  a  continuation  of  the  single  coat  of 
the  capillaries  and  the  internal  coat  of  the  arteries.  It  is  a 
simple,  homogeneous  membrane,  somewhat  thinner  than  in 
the  arteries,  lined  by  a  delicate  layer  of  epithelium. 

The  middle  coat  is  divided  by  some  into  two  layers :  an 
internal  layer,  which  is  composed  chiefly  of  longitudinal 
fibres ;  and  an  external  layer,  in  which  the  fibres  have  a  cir- 
cular direction.  These  two  layers  are  intimately  adherent, 
and  are  quite  closely  attached  to  the  internal  coat.  The 
longitudinal  fibres  are  composed  of  the  white  fibrous  tissue 
mingled  with  a  large  number  of  the  smallest  variety  of  the 
elastic  fibres.  This  layer  contains  a  large  number  of  capil- 
lary vessels  (vasa  vasorum).  The  circular  fibres  are  com- 
posed of  the  elastic  tissue,  some  of  the  same  variety  as  found 
in  the  longitudinal  layer,  some  of  medium  size,  and  some  in 
the  form  of  the  "  fenestrated  membrane."  In  addition,  there 
are  white  inelastic  fibres  interlacing  in  every  direction  and 
mingled  with  capillary  blood-vessels,  and  the  unstriped  or 
involuntary  muscular  fibres,  which  are  always  circular  in 
their  direction.  The  muscular  fibres  are  relatively  much 
less  numerous  than  in  the  arterial  system.  They  are  most 
abundant  in  the  superficial  veins. 

The  external  coat  is  generally  composed  simply  of  the 
white  fibrous  tissue,  like  the  corresponding  coat  of  the  arte- 
ries. In  the  largest  veins,  particularly  those  of  the  abdominal 


STRUCTURE   OF  THE  VEINS.  305 

cavity,  this  .coat  contains  a  layer  of  longitudinal  unstriped 
muscular  fibres.  In  the  veins  near  the  heart,  are  found  a  few 
striated  fibres,  which  are  continued  on  to  the  veins  from  the 
auricles.  In  some  of  the  inferior  animals,  as  the  turtle,  these 
fibres  are  quite  thick,  and  pulsation  of  the  veins  in  the  imme- 
diate vicinity  of  the  heart  is  very  marked. 

In  nearly  all  veins,  the  external  coat  is  several  times 
thicker  than  the  internal.  This  is  most  marked  in  the  larger 
veins,  in  which  the  middle  coat,  particularly  the  layer  of 
muscular  fibres,  is  very  slightly  developed. 

In  what  are  called  the  venous  sinuses,  and  in  the  veins 
which  pass  through  bony  tissue,  we  have  only  the  internal 
coat,  to  which  are  superadded  a  few  longitudinal  fibres,  the 
whole  closely  attached  to  the  surrounding  parts.  As  exam- 
ples of  this,  may  be  mentioned  the  sinuses  of  the  dura  mater, 
and  the  veins  of  the  large  bones  of  the  skull.  In  the  first  in- 
stance, there  is  little  more  than  the  internal  coat  of  the  vein 
firmly  attached  to  the  surrounding  layers  of  the  dura  mater. 
In  the  second  instance,  the  same  thin  membrane  is  adherent 
to  bony  canals  formed  by  a  layer  of  compact  tissue.  The 
veins  are  much  more  closely  adherent  to  the  surrounding  tis- 
sues than  the  arteries,  particularly  when  they  pass  between 
layers  of  aponeurosis.  This  fact  has  been  pointed  out  by 
Berard 1  as  very  general,  and  is  one  to  which  he  attaches 
considerable  physiological  importance.  He  considers  that 
this  arrangement  serves  to  keep  the  veins  open  and  give 
them  additional  strength. 

The  above  peculiarities  in  the  anatomy  of  the  veins  indi- 
cate considerable  differences  in  their  properties,  as  compared 
with  the  arteries.  When  a  vein  is  cut  across,  its  walls  fall 
together,  if  not  supported  by  adhesions  to  surrounding  tis- 
sues, so  that  its  caliber  is  nearly  or  quite  obliterated.  The 
yellow  elastic  tissue,  which  gives  to  the  larger  arteries  their 
great  thickness,  is  very  scanty  in  the  veins,  and  the  thin- 
walls  collapse  when  not  sustained  by  liquid  in  the  interior  of 

2  Op.  cit.,  tome  iv.,  p.  9. 
20 


306  CIRCULATION. 

the  vessels.  Whenever  the  veins  remain  open  after  section, 
it  is  on  account  of  their  attachment  to  surrounding  tissues, 
and  is  not  due  to  the  walls  of  the  vessels  themselves. 

Though  with  much  thinner  and  apparently  much  weaker 
walls,  the  veins,  as  a  rule,  will  resist  a  greater  pressure  than 
the  arteries.  Observations  on  the  relative  strength  of  the 
arteries  and  veins  were  made  by  Hales,1  but  the  most  ex- 
tended experiments  on  the  subject  were  made  by  Clifton 
Wintringham,  in  1740.3  This  observer  ascertained  that  the 
inferior  vena  cava  of  a  sheep,  just  above  the  opening  of 
the  renal  veins,  was  ruptured  by  a  pressure  of  176  pounds, 
while  the  aorta  at  a  corresponding  point  yielded  to  a  pressure 
of  158  pounds.  The  strength  of  the  portal  vein  was  even 
greater,  supporting  a  pressure  of  nearly  5  atmospheres,  bear- 
ing a  relation  to  the  vena  cava  of  6  to  5  ;  yet  these  vessels 
had  hardly  one-fifth  the  thickness  of  the  arteries.  In  the 
lower  extremities  in  the  human  subject,  the  veins  are  much 
thicker  and  stronger  than  in  other  situations,  a  provision 
against  the  increased  pressure  to  which  they  are  habitually 
subjected  in  the  upright  posture.  Wintringham  noticed  one 
singular  exception  to  the  general  rule  just  given.  In  the 
vessels  of  the  glands,  and  of  the  spleen,  the  strength  of  the 
arteries  was  much  greater  than  that  of  the  veins.  The  splenic 
vein  gave  way  under  a  pressure  of  little  more  than  one  atmos- 
phere, while  the  artery  supported  a  pressure  of  more  than 
six  atmospheres. 

A  little  reflection  on  the  influences  to  which  the  venous 
and  arterial  circulation  are  subject  will  enable  us  to  under- 
stand the  physiological  importance  of  the  great  difference  in 
the  tenacity  of  the  two  varieties  of  vessels.  It  is  true  that  in 
the  arterial  system  the  constant  pressure  is  greater  than  in 

1  Statical  Essays,  vol.  ii.,  p.  154  et  seq.      These  observations  are  not  very  sat- 
isfactory.    In  a  case  where  the  strength  of  the  carotid  and  jugular  were  com- 
pared,  in  a  mare,  the  carotid  sustained  the  greater  pressure ;  but  it  is  stated  that 
the  jugular  had  been  weakened  by  repeated  venesections. 

2  BERARD,  op.  cit.,  tome  iv.,  p.  24  et  seq. 


PKOPEETIE8   OF  THE   VEINS.  307 

the  veins ;  but  it  is  nearly  the  same  in  all  the  vessels,  and 
the  immense  extent  of  the  outlet  into  the  capillaries  provides 
against  any  very  great  increase  in  pressure,  so  long  as  the 
blood  is  in  a  condition  which  enables  it  to  pass  into  the  ca- 
pillaries. The  muscular  fibres  of  the  left  ventricle  have  but 
a  limited  power,  and  when  the  pressure  in  the  arteries  is 
such,  as  it  sometimes  is  in  asphyxia,  as  to  close  the  aortic 
valves  so  firmly  that  the  force  of  the  ventricle  will  not  open 
them,  it  cannot  be  increased.  At  the  same  time  it  is  being 
gradually  relieved  by  the  capillaries,  through  which  the  blood 
slowly  filters,  even  when  completely  unaerated.  With  the 
veins  it  is  different.  The  blood  has  a  comparatively  restrict- 
ed outlet  at  the  heart,  and  is  received  by  the  capillaries  from 
all  parts  of  the  system.  The  vessels  are  provided  with  nu- 
merous valves,  which  render  a  general  backward  action  im- 
possible. Thus,  restricted  portions  of  the  venous  system, 
from  pressure  in  the  vessels,  increase  of  fluid  from  absorption, 
accumulation  by  force  of  gravity,  and  other  causes,  may  be 
subjected  to  great  and  sudden  variations  in  pressure.  The 
great  strength  of  these  vessels  enables  them  ordinarily  to 
suffer  these  variations  without  injury ;  though  varicose  veins 
in  various  parts  present  examples  of  the  effects  of  repeated 
and  continued  distention. 

The  veins  possess  a  considerable  degree  of  elasticity, 
though  this  property  is  not  as  marked  as  it  is  in  the  arteries. 
If  we  include  between  two  ligatures  a  portion  of  a  vein  dis- 
tended with  blood,  and  make  a  small  opening  in  the  vessel, 
the  blood  will  be  ejected  with  some  force,  and  the  vessel  be- 
comes very  much  reduced  in  caliber. 

It  has  been  proven  by  direct  experiment  that  the  veins 
are  endowed  with  that  peculiar  contractility  which  is  char- 
acteristic of  the  action  of  the  unstriped  muscular  fibres.  On 
the  application  of  galvanic  or  mechanical  excitation,  they 
contract  slowly  and  gradually,  the  contraction  being  followed 
by  a  correspondingly  gradual  relaxation.  There  is  never  any 
rhythmical  or  peristaltic  movement  in  the  veins,  which  is 


308  CIRCULATION. 

competent  to  assist  the  circulation.1  The  only  regular  move- 
ments which  occur  are  seen  in  the  vessels  in  immediate  prox- 
imity to  the  right  auricle,  which  are  provided  with  a  few 
fibres  similar  to  those  which  exist  in  the  walls  of  the  heart. 

Nerves,  chiefly  from  the  sympathetic  system,  have  been 
demonstrated  in  the  walls  of  the  larger  veins,  but  have  not 
been  followed  out  to  the  smaller  ramifications. 

Valves  of  the  Veins. — The  discovery  of  the  valves  of  the 
veins  has  already  been  alluded  to  in  connection  with  the  his- 
tory of  the  discovery  of  the  circulation.  They  had  undoubt- 
edly been  observed  in  various  parts  of  the  venous  system  by 
Cananius,  and  found  very  generally  distributed  throughout 
this  system  by  Piccolomini,  the  last  named  anatomist  having 
published  an  account  of  them  in  1586 ;  but  Fabricius,  the 
greatest  anatomist  of  his  day,  had  the  good  fortune  to  dem- 
onstrate them  to  his  illustrious  pupil  William  Harvey, 
whose  immortal  discovery  indicated  their  physiological  im- 
portance. Being  ignorant  of  the  observations  of  his  prede- 
cessors on  this  subject,  Fabricius  announced  himself  as  their 
discoverer,  and  is  generally  so  regarded.  In  all  parts  of  the 
venous  system,  except,  in  general  terms,  in  the  abdominal, 
thoracic,  and  cerebral  cavities,  there  exist  little  membranous 
semilunar  folds,  resembling  the  aortic  and  pulmonic  valves  of 
the  heart.  When  distended,  the  convexities  of  these  valves 
look  toward  the  periphery.  In  the  great  majority  of  instances 
the  valves  exist  in  pairs,  but  are  occasionally  found  in  groups 
of  three.  They  are  formed  of  the  delicate  lining  membrane 
of  the  veins,  with  the  internal  or  longitudinal  layer  of  the 
middle  coat.  Some  transverse  fibres  are  found  around  the 
base  of  the  valves,  and  a  few  muscular  fibres  have  been 

1  This  statement  applies  particularly  to  the  human  subject.  Schiff  has  noticed 
rhythmical  contractions  of  the  veins  in  the  ear  of  a  rabbit  (LONGET,  Traite  de 
Physiologic,  Paris,  1861,  tome  i.,  p.  876),  and  Mr.  Wharton  Jones  has  observed 
the  same  phenomenon  in  the  wing  of  the  bat  (TODD  and  BOWMAN,  Physiological 
Anatomy,  Am.  ed.  1857,  p.  703,  note).  There  is  no  evidence  that  this  is  general, 
or  that  it  has  any  influence  in  favor  of  the  circulation. 


VALVES   OF   THE   VEINS.  300 

traced  into  their  folds.  There  exists,  also,  a  fibrous  ring  fol- 
lowing the  line  of  attachment  of  the  valvular  curtains  to  the 
vein,  which  renders  the  vessel  much  stronger  and  less  dilata- 
ble here  than  in  the  spaces  between  the  valves.  The  valves 
are  by  far  the  most  numerous  in  the  veins  of  the  lower  ex- 
tremities. They  are  generally  situated  just  below  the  point 
where  a  small  vein  empties  into  one  of  larger  size,  so  that  the 
blood,  as  it  passes  in,  finds  an  immediate  obstacle  to  passage 
in  the  wrong  direction.  The  situation  of  the  valves  may  be 
readily  observed  in  any  of  the  superficial  veins.  If  the  flow 
of  blood  be  obstructed,  little  knots  will  be  formed  in  the  con- 
gested vessels,  which  indicate  the  position  and  action  of  the 
valves.  The  simple  experiment  of  Harvey,  already  referred 
to,  presents  a  striking  illustration  of  the  action  of  the  valves. 
When  the  vein  is  thus  congested  and  knotted,  if  the  finger  be 
pressed  along  the  vessel  in  the  direction  of  the  blood  current,  a 
portion  situated  between  two  valves  may  be  emptied  of  blood ; 
but  it  is  impossible  to  empty  any  portion  of  the  vessel  by 
pressing  the  blood  in  the  opposite  direction.  On  slitting 
open  a  vein,  we  observe  the  shape,  attachment,  and  extreme 
delicacy  of  structure  of  the  valves.  When  the  vessel  is 
empty,  or  when  fluid  moves  toward  the  heart,  they  are  closely 
applied  to  the  walls ;  but  if  liquid  or  air  be  forced  in  the 
opposite  direction,  they^  project  into  its  caliber,  and  by  the 
application  of  their  free  edges  to  each  other,  effectually  pre- 
vent any  backward  current.  Fabricius  noted  the  following 
peculiarity  in  the  arrangement  of  the  valves.  When  closed, 
the  application  of  their  free  edges  forms  a  line  which  runs 
across  the  vessel ;  it  is  found  that  in  successive  sets  of  valves 
these  lines  are  at  right  angles  to  each  other,  so  that  if  in  one 
set,  this  line  has  a  direction  from  before  backwards,  in  the 
sets  above  and  below  the  lines  run  from  side  to  side. 

There  are  certain  exceptions  to  the  general  proposition 
that  the  veins  of  the  great  cavities  are  not  provided  with 
valves.  Yalves  are  found  in  the  portal  system  of  some  of 
the  inferior  animals,  as  the  horse.  They  do  not  exist,  how- 


310  CrRCULATTOK". 

ever,  in  this  situation  in  the  human  subject.  Generally,  in 
following  out  the  branches  of  the  inferior  vena  cava,  no 
valves  are  found  until  we  come  to  the  crural  vein ;  but  occa- 
sionally there  is  a  double  valve  at  the  origin  of  the  external 
iliac.  In  some  of  the  inferior  animals,  there  exists  constantly 
a  single  valvular  fold  in  the  vena  cava  at  the  openings  of  the 
hepatic,  and  one  at  the  opening  of  the  renal  vein.  This  is 
not  constant  in  the  human  subject.1  Valves  are  found  in  the 
spermatic,  but  not  in  the  ovarian  veins.  A  single  valvular 
fold  has  been  described  by  Dr.  J.  H.  Brinton,  at  the  opening 
of  the  right  spermatic  into  the  vena  cava.8  There  are  two 
valves  in  the  azygos  vein  near  its  opening  into  the  superior 
vena  cava.  There  is  a  single  valve  at  the  orifice  of  the 
coronary  vein.  There  are  no  valves  at  the  openings  of  the 
brachio-cephalic  into  the  superior  vena  cava ;  but  there  is  a 
strong  double  valve  at  the  point  where  the  internal  jugular 
opens  into  the  brachio-cephalic.  Between  this  point  and  the 
capillaries  of  the  brain,  the  vessels  are  entirely  deprived  of 
valves,  except  in  very-  rare  instances,  when  one  or  two  are 
found  in  the  course  of  the  jugular. 

In  addition  to  the  double,  or  more  rarely  triple,  valves 
which  have  just  been  described,  there  is  another  variety, 
found  in  certain  parts,  at  the  point  where  a  tributary  vein 
opens  into  a  main  trunk.  This  consists  of  a  single  fold  which 
is  attached  to  the  smaller  vessel,  but 'projects  into  the  larger. 
Its  action  is  to  prevent  regurgitation,  by  the  same  mechanism 
as  the  ileo-csecal  valve  prevents  the  passage  of  matter  from 
the  large  into  the  small  intestine.  These  vajves  are  much 
less  numerous  than  the  first  variety. 

1  Dr.  Crisp,  of  England,  has  described  valves  in  the  splenic  veins  in  some  of 
the  inferior  animals.  In  one  of  the  mesenteric  veins  of  the  reindeer,  he  showed 
forty-two  pairs  of  valves  (New  York  Medical  Journal,  April,  1865,  p.  67). 

a  Description  of  a  Valve  at  the  Termination  of  the  Right  Spermatic  Vein 
in  the  Vena  Cava,  with  Remarks  on  its  Relations  to  Varicocele.  By  JOHN  H. 
BRINTON,  M.  D.  American  Journal  of  the  Medical  Sciences,  July,  1856.  The 
presence  of  this  valve,  according  to  Dr.  Brinton,  explains  the  more  frequent  oc- 
currence of  varicocele  on  the  right  side. 


COURSE   OF  THE  BLOOD  IN  THE  VEINS.  311 

The  veins  form  a  system  which  is  adapted  to  the  re- 
turn of  blood  to  the  heart  in  a  comparatively  slow  and 
unequal  current.  Distention  of  certain  portions  is  pro- 
vided for ;  and  the  vessels  are  so  protected  with  valves, 
that  whatever  influences  the  current  must  favor  its  flow  in 
the  direction  of  the  heart.  It  is  a  system  which  is  cal- 
culated to  receive  the  blood  from  the  parts  after  it  has 
become  unfit  for  nutrition,  and  pass  it  in  the  requisite 
quantity  to  the  lungs,  through  the  right  side  of  the  heart, 
for  regeneration. 

Course  of  the  Blood  in  the  Veins. — The  experiments  of 
Hales  and  Sharpey,  showing  that  defibrinated  blood  can  be 
made  to  pass  from  the  arteries  into  the  capillaries  and  out  at 
the  veins  by  a  pressure  less  than  that  which  exists  in  the 
arterial  system,  and  the  observations  of  Magendie  upon  the 
circulation  in  the  leg  of  a  living  dog,  showing  that  ligation 
of  the  artery  arrests  the  flow  in  the  vein,  points  which  have 
already  been  fully  discussed  in  treating  of  the  causes  of  the 
capillary  circulation,  have  established,  beyond  question,  the 
fact  that  the  force  exerted  by  the  left  ventricle  is  sufficient  to 
account  for  the  venous  circulation.  The  heart  must  be  con- 
sidered the  prime  cause  of  all  movement  in  these  vessels. 
Regarding  this  as  definitely  ascertained,  there  remain  to  con- 
sider, in  the  study  of  the  course  of  the  blood  in  the  veins,  the 
character  of  the  current,  the  influence  of  the  vessels  them- 
selves, and  the  question  of  the  existence  of  forces  which  may 
assist  the  vis  a  tergo  from  the  heart,  and  circumstances  which 
may  interfere  with  the  flow  of  blood. 

As  a  rule,  in  the  normal  circulation,  the  flow  of  blood  in 
the  veins  is  continuous.  The  intermittent  impulse  of  the 
heart,  which  progressively  diminishes  as  we  recede  from  this 
organ,  but  is  still  felt  even  in  the  smallest  arteries,  is  lost,  as 
we  have  seen,  in  the  capillaries.  Here,  for  the  first  time,  the 
blood  moves  in  a  constant  current ;  and  as  the  pressure  in  the 
arteries  is  continually  supplying  fresh  blood,  that  which  has 


312  CIRCULATION. 

circulated  in  the  capillaries  is  forced  into  the  venous  radicles 
in  a  steady  stream.  As  the  supply  to  the  capillaries  of  differ- 
ent parts  is  regulated  by  the  action  of  the  small  arteries,  and 
as  this  supply  is  subject  to  great  variations,  there  must  neces- 
sarily be  corresponding  variations  in  the  intensity  of  the 
current  in  the  veins,  and  the  quantity  of  blood  which  these 
vessels  receive.  As  we  should  anticipate,  then,  the  venous 
circulation  is  subject  to  very  great  variations  arising  from  ir- 
regularity in  the  supply  of  blood,  aside  from  any  action  of 
the  vessels  themselves,  or  any  external  disturbing  influences. 
A  great  variation  in  the  venous  current  is  observed  in  the 
veins  which  collect  the  blood  from  the  intestinal  canal. 
During  the  intervals  of  digestion,  these  vessels  carry  a  com- 
paratively small  quantity  of  blood;  but  during  digestion, 
they  are  laden  with  the  fluids  received  by  absorption,  and  the 
quantity  is  immensely  increased. 

It  often  happens  that  a  vein  becomes  obstructed  from 
some  cause  which  is  entirely  physiological,  as  the  action  of 
muscles.  The  immense  number  of  veins,  as  compared  with 
the  arteries,  and  their  free  communications  with  each  other, 
provide  that  the  current,  under  these  circumstances,  is  sim- 
ply diverted,  passing  to  the  heart  by  another  channel.  When 
any  part  of  the  venous  system  is  distended,  the  vessels  react 
on  the  blood,  and  exert  a  certain  influence  on  the  current, 
always  pressing  it  toward  the  heart,  for  the  valves  oppose  the 
flow  in  the  opposite  direction. 

The  intermittent  action  of  the  heart,  which  pervades  the 
whole  arterial  system,  is  generally  absorbed,  as  it  were,  in 
the  passage  of  the  blood  through  the  capillaries  ;  but  when 
the  arterioles  of  any  part  are  very  much  relaxed,  the  impulse 
of  the  central  organ  may  extend  to  the  veins.  Bernard  has 
shown  this  in  the  most  striking  manner,  in  his  well-known 
experiments  on  the  circulation  in  the  glands.1  When  the 
glands  are  in  physiological  activity,  the  quantity  of  blood 

1  BERNARD,  Liquides  de  V  Organisme,  Paris,  tome  i.,  p.  301 ;  and  Journal  de 
tAnatomie  ct  de  la  Physiologic,  Septembre,  1864,  p.  507  et  seq. 


COURSE   OF  THE  BLOOD  W  THE  VEINS.  313 

which  they  receive  is  very  much  increased.  It  is  then  fur- 
nished to  supply  material  for  the  secretion,  and  not  exclu- 
sively for  nutrition.  If  the  vein  be  opened  at  such  a  time,  it 
is  found  that  the  blood  has  not  lost  its  arterial  character,  that 
the  quantity  which  escapes  is  much  increased,  and  the  flow 
is  in  an  intermittent  jet,  as  from  a  divided  artery.  This  is 
due  to  the  relaxed  condition  of  the  arterioles  of  the  part,  and 
the  phenomenon  thus  observed  is  the  true  venous  pulse. 
"What  thus,  occurs  in  a  restricted  portion  of  the  circulatory 
system  may  take  place  in  all  the  veins,  though  in  a  less 
marked  degree.  Physicians  have  frequently  noticed,  after 
the  blood  has  been  flowing  for  some  time,  in  the  operation  of 
venesection,  that  the  color  changes  from  black  to  red,  and 
the  stream  becomes  intermittent,  often  leading  the  operator 
to  fear  that  he  has  pricked  the  artery.  In  all  probability 
the  phenomenon  is  due  to  the  relaxation  of  the  arterioles,  as 
one  of  the  effects  of  abstraction  of  blood,  producing  the 
same  condition  that  has  been  noted  in  some  of  the  glands 
during  their  functional  activity.  The  hypothesis  that  it  is 
due  to  an  impulse  from  the  adjacent  artery  is  not  admissible. 
Except  in  the  veins  near  the  heart,  any  pulsation  which  oc- 
curs is  to  be  attributed  to  the  force  of  the  heart,  transmitted 
with  unusual  facility  through  the  capillary  system.  A  nearly 
uniform  current,  however,  is  the  rule,  and  a  marked  pulsation 
the  rare  exception.  Mr.  T.  "W.  King,  in  an  article  on  the 
"  Safety-Yalve  of  the  Human  Heart,"  *  discussing  the  forces 
which  concur  to  produce  the  venous  circulation,  mentions 
the  fact  that  in  some  individuals,  after  a  full  meal,  pulsation 
can  be  observed  in  the  veins  of  the  hand  or  the  median  veins 
of  the  forehead.  This  phenomenon  is  very  delicate,  and,  to 
make  it  more  apparent,  he  employed  a  thread  of  black  seal- 
ing wax  about  two  inches  long,  which  was  fixed  across  the 
vein  of  the  back  of  the  hand  with  a  little  tallow,  so  as  to 
make  a  long  and  excessively  light  lever,  capable  of  indicating 
a  very  slight  movement  in  the  vessel.  In  this  way  he  dem- 

1  Guy's  Hospital  Reports,  1837. 


314  CIRCULATION. 

onstrated  pulsation  in  the  veins  of  the  hand,  and  also  in 
the  arm,  foot,  and  leg.  These  movements  are  very  slight,, 
and  are  generally  only  appreciable  by  some  such  delicate 
means  of  investigation.  This  is  a  strong  argument  in  oppo- 
sition to  the  opinion  of  those  who  regard  the  action  of  the 
heart  as  inoperative  in  the  veins.  In  certain  cases  of  disease, 
Mr.  King  has  noted  very  marked  pulsation  in  the  veins  of 
the  back  of  the  hand,  and  other  vessels  far  removed  from 
the  heart. 

Pressure  of  Blood  in  the  Veins. — The  pressure  in  the 
veins  is  always  much  less  than  in  the  arteries.  It  is  exceed- 
ingly variable  in  different  parts  of  the  venous  system,  and  in 
the  same  part  at  different  times.  As  a  rule,  it  is  in  inverse 
ratio  to  the  arterial  pressure.  Whatever  favors  the  passage 
of  blood  from  the  arteries  into  the  capillaries  has  a  tendency 
to  diminish  the  arterial  pressure ;  and,  as  it  increases  the 
quantity  of  blood  which  passes  into  the  veins,  must  increase 
the  venous  pressure.  The  great  capacity  of  the  venous  sys- 
tem, its  numerous  anastomoses,  the  presence  of  valves  which 
may  shut  off  a  portion  from  the  rest,  are  circumstances  which 
involve  great  variations  in  pressure  in  different  vessels.  It 
has  been  ascertained  by  Yolkmann,  and  this  has  been  con- 
firmed by  others,  that  as  a  rule  the  pressure  is  diminished  as 
we  pass  from  the  periphery  toward  the  heart.  In  an  obser- 
vation on  the  calf,  he  found  that  with  a  pressure  of  about  6'5 
inches  of  mercury  in  the  carotid,  the  pressure  in  the  meta- 
tarsal  vein  was  1*1  inch,  and  but  O36  in  the  jugular.1  The 
pressure  is,  of  course,  subject  to  certain  variations.  Muscular 
effort  has  a  marked  influence  on  the  force  of  the  circulation 
in  certain  veins,  and,  consequently,  in  these  vessels  produces 
an  elevation  in  the  pressure.  As  the  reduced  pressure  in  the 
veins  is  due  in  a  measure  to  the  great  relative  capacity  of 
the  venous  system,  and  the  free  communications  between  the 
vessels,  it  would  seem  that  if  it  were  possible  to  reduce  the 

1  MILNE-EDWARDS,  Lepons  sur  la  Physiologic,  Paris,  1859,  tome  iv.,  p.  329. 


CAUSES   OF  THE  VENOUS   CIRCULATION.  315 

capacity  of  the  veins  in  a  part,  and  force  all  the  blood  to 
pass  to  the  heart  by  a  single  vessel  corresponding  to  the  ar- 
tery, the  pressure  in  this  vessel  should  be  greatly  increased. 
Poiseuille  has  shown  this  to  be  the  fact  by  the  experiment  of 
ligating  all  the  veins  coming  from  a  part,  except  one,  which 
had  the  volume  of  the  artery  by  which  the  blood  was  sup- 
plied, forcing  all  the  blood  to  return  by  this  single  channel. 
This  being  done,  he  found  the  pressure  in  the  vein  immensely 
increased,  becoming  nearly  equal  to  that  in  the  artery.1 

Rapidity  of  the  Venous  Circulation. — It  is  impossible  to 
fix  upon  any  definite  rate  as  representing  the  rapidity  of  the 
current  of  blood  in  the  veins.  It  will  be  seen  that  various 
circumstances  are  capable  of  increasing  very  considerably  the 
rapidity  of  the  flow  in  certain  veins,  and  that  under  certain  con- 
ditions the  current  in  some  parts  of  the  venous  system  is  very 
much  retarded.  Undoubtedly  the  general  movement  of  blood 
in  the  veins  is  very  much  slower  than  in  the  arteries,  from 
the  fact  that  the  quantity  of  blood  is  greater.  If  it  be  as- 
sumed that  the  quantity  of  blood  in  the  veins  is  double  that 
contained  in  the  arteries,  the  general  average  of  the  current 
would  be  diminished  one-half.  As  we  near  the  heart,  how- 
ever, the  flow  becomes  more  uniform,  and  progressively  in- 
creases in  rapidity. 

As  the  effect  of  the  heart's  action  upon  the  venous  circu- 
lation is  subject  to  so  many  modifying  influences  through  the 
small  arteries  and  capillaries,  and  as  there  are  other  forces 
influencing  the  current,  which  are  by  no  means  uniform  in 
their  action,  with  our  present  knowledge,  estimates  of  the 
general  rapidity  of  the  venous  circulation,  or  the  variations 
in  different  vessels,  would  be  founded  on  mere  speculations. 

Causes  of  the  Venous  Circulation. 

In  the  veins,  the  blood  is  farthest  removed  from  the  influ- 
ence of  the  contractions  of  the  left  ventricle ;  and  though 

1  BERARD,  Cows  de  Physiologic,  Paris,  1855,  tome  iv.,  p.  21. 


316  CIRCULATION. 

these  are  felt,  there  are  many  other  causes  which  combine  to 
carry  on  the  circulation,  and  many  influences  by  which  it  is 
retarded  or  obstructed. 

The  great  and  uniform  force  which  operates  on  the  circu- 
lation in  these  vessels  is  the  vis  a  tergo.  We  have  repeatedly 
referred  to  the  entire  adequacy  of  the  arterial  pressure,  prop- 
agated through  the  capillaries,  to  account  for  the  movement  of 
blood  in  the  veins,  provided  there  be  no  very  great  obstacles 
to  the  current.  There  are  no  facts  which  lead  us  to  doubt  the 
operation  of  this  force  as  the  prime  cause  of  the  venous  circula- 
tion ;  and  the  only  question  which  arises  is  whether  there  be 
any  force  exerted  in  the  capillaries  themselves  which  is  super- 
added  to  the  force  of  the  heart.  In  discussing  the  capillary 
circulation,  there  has  been  found  no  direct  proof  of  the  exist- 
ence of  a  distinct  "  capillary  power "  influencing  the  move- 
ment of  blood  in  these  vessels ;  and  consequently  all  the  vis 
a  tergo  operating  on  the  circulation  in  the  veins  must  be 
attributed  to  the  action  of  the  left  ventricle. 

The  other  forces  which  concur  to  produce  movement  of 
blood  in  the  veins  are  : 

1.  Muscular  action,  by  which  many  of  the  veins  are  at 
times  compressed,  thus  forcing  the  blood  toward  the  heart, 
regurgitation  being  prevented  by  the  action  of  the  valves. 

2.  A  suction  force  exerted  by  the  action  of  the  thorax  in 
respiration;  operating,  however,  only  on  the  veins  in  the 
immediate  neighborhood  of  the  chest. 

3.  A  possible  influence  in  the  contraction  of  the  coats  of 
the  vessels  themselves.     This  is  marked  in  the  veins  near  the 
heart,  in  some  of  the  inferior  animals. 

4.  The  force  of  gravity,  which  operates  only  on  vessels 
which  carry  blood  from  above  downward  to  the  heart ;  and 
a  little  suction  force  which  may  be  exerted  upon  the  blood  in 
a  small  vein  as  it  passes  into  a  larger  vessel  in  which  the 
current  is  more  rapid. 

The  obstacles  to  the  venous  circulation  are:  Pressure 
sufficient  to  obliterate  the  caliber  of  a  vessel,  when,  from  the 


CAUSES   OF  THE  VENOUS   CIRCULATION.  317 

free  communication  with  other  vessels,  the  current  is  simply 
diverted  into  another  channel ;  the  expulsive  efforts  of  res- 
piration ;  the  contractions  of  the  right  side  of  the  heart ;  and 
the  force  of  gravity,  which  operates,  in  the  erect  posture,  on 
the  current  in  all  excepting  the  veins  of  the  head,  neck,  and 
parts  of  the  trunk  above  the  heart. 

Influence  of  Muscular  Contraction. — That  the  action  of 
muscles  has  a  considerable  influence  on  the  current  of  blood 
in  the  veins  situated  between  them,  and  in  their  substance,  has 
long  been  recognized.  It  is  exemplified  in  the  operation  of 
venesection,  when  it  is  well  known  that  the  jet  from  the  vein 
may  be  very  much  increased  in  force  by  contraction  of  the 
muscles  below  the  opening.  This  action  is  so  marked,  that 
the  parts  of  the  venous  system  which  are  situated  in  the  sub- 
stance of  muscles  have  been  compared  by  Chassaignac  to  a 
sponge  full  of  liquid,  vigorously  pressed  by  the  hand.1  It 
must  always,  be  remembered,  however,  that  though  the 
muscles  are  capable  of  acting  on  the  blood  contained  in  veins 
in  their  substance  with  great  vigor,  the  heart  is  fully  capable 
of  producing  the  venous  circulation  without  their  aid ;  a  fact 
which  is  exemplified  in  a  striking  manner  in  the  venous  cir- 
culation in  paralyzed  parts. 

It  has  been  shown  by  actual  observations  with  the  hemo- 
dynamometer,  that  muscular  action  is  capable  of  immensely 
increasing  the  pressure  in  certain  veins.  The  first  definite 
experiments  on  this  subject  were  made  by  Magendie,  who 
showed  a  pressure  of  over  two  inches  of  mercury  produced 
by  a  general  muscular  contraction,  on  the  passage  of  a  gal- 
vanic current  from  a  needle  plunged  into  the  cervical  region 
of  the  spinal  marrow  to  one  fixed  in  the  muscles  of  the  thigh.2 
The  experiments  of  Bernard  have  shown  this  more  accurately. 
This  physiologist  found  that  the  pressure  in  the  jugular  of  a 
horse,  in  repose,  was  1-4  inch ;  but  the  action  of  the  muscles  in 

1  BERARD,  op.  tit.,  tome  iv.,  p.  57. 

9  MAGENDIE,  Phenomena  Physiques  dela  Vie,  Paris,  1842,  tome  iii,  p.  163. 


31 8  CIRCULATION. 

raising  the  head  increased  it  to  a  little  more  than  five  inches, 
or  nearly  four  times.1  These  observations  show  at  once  the 
great  variations  in  the  venous  current,  and  the  important 
influence  of  muscular  contraction  on  the  circulation. 

In  order  that  contractions  of  muscles  shall  assist  the 
venous  circulation,  two  things  are  necessary  : 

1.  The  contraction  must  be  intermittent.     This  is  always 
the  case  in  the  voluntary  muscles.     It  is  a  view  entertained 
by  many  that  each  muscular  fibre  relaxes  immediately  after 
its  contraction,  which  is  instantaneous,  and  that  a  certain 
period  of  repose  is  necessary  before  it  can  contract  again. 
However  this  may  be,  it  is  well  known  that  all  active  mus- 
cular contraction,  as  distinguished  from  the  efforts  necessary 
to  maintain  the  body  in  certain  ordinary  positions,  is  inter- 
mittent, and  not  very  prolonged.     Thus  the  veins,  which  are 
partly  emptied  by  the  compression,  are  filled  again  during 
the  repose  of  the  muscle. 

2.  There  should  be  no  possibility  of  a  retrograde  move- 
ment of  the  blood.     This  condition  is  fulfilled  by  the  action 
of  the  valves.     Anatomical  researches  have  shown  that  these 
valves  are  most  abundant  in  veins  situated  in  the  substance 
of  or  between  the  muscles,  and  that  they  do  not  exist  in  the 
veins  of  the  cavities,  which  are  not  subject  to  the  same  kind 
of  compression.     It  is  thus  that  the  blood  is  prevented  from 
passing  backward  toward  the  capillary  system ;  and  when 
the  caliber  of  a  vein  is  reduced  by  compression,  part  of  its 
contents  must  be  forced  toward  the  heart.     This  action  of 
the  valves  constitutes  their  most  important  function. 

Milne-Edwards  alludes  to  an  important  physiological 
bearing  of  the  acceleration  of  the  venous  circulation  by  con- 
tractions of  muscles,  on  their  nutrition.2  It  is  apparently 
necessary  that  the  supply  of  blood  should  be  increased  in  a 
muscle,  in  proportion  to  and  during  its  activity ;  for  at  that 

1  BERNARD,  Lemons  sur  la  Physiologic  et  la  Pathologie  du  Sysleme  Nerveux^ 
Paris,  1858,  tome  i.,  p.  285. 

*  Lefons  sur  la  Physiologic,  tome  iv.,  p.  310. 


CAUSES   OF  THE   VENOUS   CIRCULATION.  319 

time  its  destructive  assimilation  is  undoubtedly  augmented, 
and  there  is  an  increased  demand  on  the  blood  to  supply  the 
waste.  It  is  apparently  a  provision  of  Nature  that  the  ac- 
tivity of  a  muscle,  facilitating  the  passage  of  blood  in  its 
veins,  and  consequently  its  flow  from  the  capillaries,  induces 
an  increased  supply  of  the  nutrient  fluid.  As  the  develop- 
ment of  tissues  is  generally  in  proportion  to  their  vascularity, 
this  may  account  for  the  increase  in  the  development  of 
muscles,  which  is  the  invariable  result  of  continued  exercise. 

Force  of  Aspiration  from  the  Thorax. — During  the  act 
of  inspiration,  the  enlargement  of  the  thorax,  by  depression 
of  the  diaphragm  and  elevation  of  the  ribs,  affects  the  move- 
ments of  fluids  in  all  the  tubes  in  its  vicinity.  The  air  rushes 
in  by  the  trachea  and  expands  the  lungs,  so  that  they  follow 
the  movements  of  the  thoracic  walls.  The  flow  of  blood  into 
the  great  arteries  is  somewhat  retarded,  as  is  indicated  by 
the  diminution  in  the  arterial  pressure ;  and  finally,  the  blood 
in  the  great  veins  passes  to  the  heart  with  greater  facility, 
and  in  increased  quantity.  This  last-mentioned  phenomenon 
can  be  easily  observed,  when  the  veins  are  prominent,  in  pro- 
found or  violent  inspiration.  The  veins  at  the  lower  part  of 
the  neck  are  then  seen  to  empty  themselves  of  blood  during 
the  inspiration,  and  become  distended  during  expiration, 
producing  a  sort  of  pulsation  which  is  synchronous  with  res- 
piration. This  can  always  be  observed  after  exposure  of  the 
jugular  in  the  lower  part  of  the  neck  in  an  inferior  animal. 
After  this  operation,  if  we  cause  the  animal  to  make  violent 
respiratory  efforts,  the  vein  will  be  'almost  emptied  and  col- 
lapsed with  inspiration,  and  turgid  with  expiration.  The 
movements  of  the  veins  near  the  thorax  have  long  been  ob- 
served and  described  with  tolerable  accuracy.  By  the  fol- 
lowing simple  yet  conclusive  experiment,  the  regular  action 
of  the  suction  force  was  demonstrated  by  Magendie.  Having 
introduced  a  gum-elastic  sound  into  the  jugular  vein  of  a  dog, 
and  passed  it  down  to  the  right  auricle,  he  saw  "  that  the 


320  CIRCULATION. 

blood  flowed  from  the  extremity  of  the  sound  only  in  the 
moment  of  expiration.  We  obtain  results  entirely  analogous 
if  we  introduce  the  sound  into  the  crural  vein,  directing  it 
toward  the  abdomen." l  As  several  contractions  of  the  right 
auricle  occur  between  two  acts  of  respiration,  it  is  shown  by 
this  experiment  that,  during  inspiration,  the  suction  force  is 
sufficient  to  counterbalance  the  contractions  of  the  auricle, 
which  would  otherwise  force  a  certain  quantity  of  blood 
through  the  soiind,  as  it  does  during  expiration  ;  for  then  we 
have  a  jet  synchronous  with  the  beats  of  the  heart.  Cathe- 
terization  of  the  right  side  of  the  heart  is  now  quite  a  common 
experiment ;  and  we  have  frequently  observed  the  variations 
in  the  flow  of  blood  from  a  sound  introduced  through  the 
jugular,  which  were  mentioned  by  Magendie.  The  suction 
force  is  still  more  strikingly  exhibited  in  this  operation  by 
the  entrance  of  air,  which  is  frequently  drawrn  into  the  heart 
during  a  violent  inspiration. 

The  influence  of  aspiration  on  the  circulation  in  the  veins 
was  still  more  minutely  studied  in  1825  by  Barry,  whose 
most  important  experiments  have  been  repeated,  with  some 
modifications,  by  Poiseuille.  Barry  introduced  through  the 
jugular  of  a  horse  a  bent  tube  of  glass,  one  extremity  being 
passed  into  the  right  cavities  of  the  heart,  or  the  vena  cava, 
and  the  other  into  a  vessel  containing  a  colored  liquid.  He 
found  that  with  each  act  of  inspiration  the  liquid  mounted 
up  in  the  tube,  demonstrating  the  operation  of  a  notable  suc- 
tion force.  The  observations  and  experiments  of  Barry  were 
made  on  quite  an  extended  scale,  but  many  of  his  conclusions 
were  not  entirely  warranted.  He  studied,  for  example,  the 
effect  of  preventing  the  entrance  of  air  into  the  chest  by  the 
trachea,  and  found  that  this  increased  the  suction  force  very 
considerably,  as  indicated  by  the  greater  elevation  of  liquid 
in  the  tube  with  each  inspiratory  effort ;  but  he  supposed 

1  MAGENDIE,  Influences  des  Mouvements  de  la  Poitrine  et  des  Efforts  sur  la  Cir- 
culation du  Sang.— Journal  de  Physiologic  Experimentale,  Paris,  1821,  tome  i.; 
p.  136. 


CAUSES   OF  THE  VENOUS   CIRCULATION.  321 

that  this  force  from  the  thorax  was  felt  in  the  entire  venous 
system,  an  opinion  which,  as  we  shall  see,  the  most  simple 
observations  have  shown  to  be  entirely  erroneous.1  As  this 
force  is  not  felt  throughout  the  whole  of  the  venous  system, 
it  becomes  a  question  of  interest  to  determine  how  far  its  in- 
fluence extends,  and  why  it  is  restricted  to  certain  vessels. 
Like  the  action  of  the  muscular  system  on  certain  veins,  it  is 
simply  superadded  to  the  force  of  the  heart,  the  latter  being 
entirely  competent  to  keep  up  the  venous  circulation.  A 
proof  that  it  is  not  essential  is  seen  in  the  fact  that  the  circu- 
lation is  effected  in  animals  which  do  not  inspire,  but  swallow 
their  air,2  and  in  the  foetus,  before  any  movements  of  respi- 
ration take  place. 

Direct  observations  on  the  jugulars  show  conclusively  that 
the  influence  of  inspiration  cannot  be  felt  much  beyond  these 
vessels.  They  are  seen  to  collapse  with  each  inspiratory  act, 
a  condition  which  limits  this  influence  to  the  veins  near  the 
heart.  The  flaccidity  of  the  walls  of  the  veins  will  not  permit 
the  extended  action  of  any  suction  force.  If  a  portion  of  a  vein 
removed  from  the  body  be  attached  to  the  nozzle  of  a  syringe, 
and  we  attempt  to  draw  a  liquid  through  it,  though  the  suc- 
tion force  be  applied  very  gently,  when  the  vessel  has  any 
considerable  length,  its  walls  will  be  drawn  together.  In  the 
circulation,  the  veins  are  moderately  distended  with  blood  by 
the  vis  a  tergo,  and,  to  a  certain  extent,  supported  by  con- 
nections with  surrounding  tissues,  so  that  the  force  of  aspira- 
tion is  felt  farther  than  in  any  experiment  on  vessels  re- 
moved from  the  body.  The  blood,  as  it  approaches  the 
thorax,  impelled  by  other  forces,  is  considerably  accelerated 
in  its  flow  ;  but  it  is  seen  by  direct  observation,  that  beyond 

1  BARRY,  Recherches  Experimentales  sur  les  Causes  du  Mouvement  du  Sang  dans 
les  Vdnes,  Paris,  1825,  p.  12  et  &eq. 

2  In  many  animals  that  take  the  air  into  the  lungs  by  an  act  like  that  of  de- 
glutition, there  are  regular  pulsations  in  the  veins  near  the  heart,  which  are  quite 
abundantly  provided  with  muscular  fibres  like  those  found  in  the  heart.     It  is  a 
question  whether  this  does  not  take  the  place  of  the  suction  force  from  the  chest,, 
which  operates  in  other  animals. 

21 


322  CIRCULATION. 

a  certain  point,  and  that  very  near  the  chest,  ordinary  aspi- 
ration has  no  influence,  and  violent  efforts  rather  retard  than 
favor  the  current. 

In  the  liver,  the  influence  of  inspiration  becomes  a  very 
important  element  in  the  production  of  the  circulation. 
This  organ  presents  a  vascular  'arrangement  which  is  excep- 
tional. The  blood,  distributed  by  the  arteries  in  a  capillary 
plexus  in  the  mucous  membrane  of  the  alimentary  canal  and 
in  the  spleen,  instead  of  being  returned  directly  to  the  heart 
by  the  veins,  is  collected  into  the  portal  vein,  carried  to  the 
liver,  and  there  distributed  in  a  second  set  of  capillary  vessels. 
It  is  then  collected  in  the  hepatic  veins,  and  carried  by  the 
vena  cava  to  the  heart.  This  double  capillary  plexus  be- 
tween the  left  and  right  sides  of  the  heart  has  been  cited  as 
an  argument  against  the  fact  that  the  left  ventricle  is  capable 
of  sending  the  blood  through  the  entire  circuit  of  the  vascu- 
lar system.  The  three  hepatic  veins  open  into  the  inferior 
vena  cava  near  the  point  where  it  passes  the  diaphragm, 
where  the  force  of  aspiration  from  the  thorax  would  mate- 
rially assist  the  current  of  blood.  On  following  these  vessels 
into  the  substance  of  the  liver,  it  is  found  that  their  walls  are 
so  firmly  adherent  to  the  tissue  of  the  organ,  that,  when  cut 
across,  they  remain  patulous ;  and  it  is  evident  that  they  re- 
main open  under  all  conditions.  The  thorax  can  therefore 
exert  a  powerful  influence  upon  the  hepatic  circulation; 
for  it  is  only  the  flacci-dity  of  the  walls  of  the  vessels  which 
prevents  this  influence  from  operating  throughout  the  entire 
venous  system. 

Though  this  must  be  a  very  important  element  in  the 
production  of  the  circulation  in  the  liver,  the  fact  that  the 
blood  circulates  in  this  organ  in  the  foetus  before  any  move- 
ments of  the  thorax  take  place,  shows'  that  it  is  not  absolute- 
ly essential.  All  of  the  influences  which  we  have  thus  far 
considered  are  merely  supplementary  to  the  action  of  the 
great  central  organ  of  the  circulation. 

A  further  proof,  if  any  were  needed,  of  the  suction  force 


AIR   IN   THE   VEINS.  323 

of  inspiration  is  found  in  an  accident  which  is  not  infrequent 
in  surgical  operations  in  the  lower  part  of  the  neck.  "When 
the  veins  in  this  situation  are  kept  open  by  a  tumor,  or  by 
induration  of  the  surrounding  tissues,  an  inspiratory  effort 
has  occasionally  been  followed  by  the  entrance  of  air  into  the 
circulation ;  an  accident  which  is  liable  to  lead  to  the  gravest 
results.  This  occurs  only  when  a  divided  vein  is  kept  patu- 
lous  ;  and  the  accident  proves  both  the  influence  of  inspira- 
tion on  liquids  in  the  veins  near  the  chest,  and  its  restriction 
to  the  vessels  in  this  particular  situation  by  the  flaccidity  of 
their  walls.  The  conditions  under  which  this  occurs  may  be 
imitated  in  the  lower  animals  by  introducing  a  tube  through 
the  vein  into  the  thorax;  when,  with  a  violent  act  of  inspi- 
ration, air  will  be  drawn  in,  and  the  curious  and  startling 
effects  upon  the  circulation  may  be  observed. 

A  full  discussion  of  the  subject  of  air  in  the  veins,  which 
is  of  great  pathological  interest,  does  not  belong  to  the  domain 
of  physiology.  The  blood  is  capable  of  dissolving  a  certain 
quantity  of  atmospheric  air ;  and  a  small  quantity,  very  grad- 
ually introduced  into  a  vein,  can  be  disposed  of  in  this  way. 
When,  however,  a  considerable  quantity  suddenly  finds  its 
way  into  the  venous  system,  the  patient,  or  animal,  experi- 
ences a  sense  of  mortal  distress,  and  almost  immediately  falls 
into  a  state  of  insensibility.  A  peculiar  whistling  sound  is 
heard  when  the  air  passes  in ;  and  if  the  ear  be  applied  to  the 
chest,  we  distinguish  the  labored  efforts  of  the  heart,  accom- 
panied by  a  loud  churning  sound.  On  opening  the  chest 
after  death,  the  right  cavities  of  the  heart  are  invariably 
found  distended  with  air  and  blood ;  the  blood  being  frothy 
and  florid.  Generally  the  left  side  of  the  heart  is  nearly  or 
quite  empty. 

The  production  of  death  from  air  in  the  veins  is  purely 
mechanical.  The  air,  finding  its  way  to  the  right  ventricle, 
is  mixed  with  the  blood  in  the  form  of  minute  bubbles,  and 
passed  into  the  pulmonary  artery.  Once  in  this  vessel,  it  is 
impossible  for  it  to  pass  through  the  capillaries  of  the  lungs, 


324:  CIRCULATION. 

and  death  by  suffocation  is  the  inevitable  result,  if  the  quan- 
tity of  air  be  large.  It  is  because  no  blood  can  pass  through 
the  lungs,  that  the  left  cavities  of  the  heart  are  usually  found 
empty. 

Certain  cases  of  entrance  ef  air  into  the  veins  in  surgical 
operations,  though  presenting  the  most  alarming  immediate 
symptoms,  have  terminated  in  recovery.  In  these  instances, 
the  quantity  of  air  is  not  sufficient  to  completely  block  up 
the  pulmonary  capillaries,  and  it  is  gradually  absorbed  by 
the  blood. 

Air  injected  into  the  arteries  produces  no  such  serious  ef- 
fects as  air  in  the  veins.  It  is  arrested  in  the  capillaries  of 
certain  parts,  and  in  the  course  of  time  is  absorbed  without 
having  produced  any  injury. 

Aside  from  the  pressure  exerted  by  the  contraction  of 
muscles,  and  the  force  of  aspiration  from  the  thorax,  the  in- 
fluences which  assist  the  venous  circulation  are  very  slight. 
As  far  as  the  action  of  the  coats  of  the  vessels  themselves  is 
concerned,  their  contraction,  it  must  be  remembered,  is  slow 
and  gradual,  like  the  contraction  of  the  arteries ;  and  it  is 
hardly  possible  that  in  the  general  venous  system  it  should 
operate  at  all  on  the  blood-current,  beyond  the  simple  influ- 
ence of  the  reduction  of  the  caliber  of  the  vessel.  There  is 
a  slight  contraction  in  the  vense  cavse,  in  the  immediate 
proximity  of  the  heart,  which  is  very  much  more  extended 
in  many  of  the  lower  vertebrate  animals,  and  may  be  men- 
tioned as  having  an  influence,  very  insignificant  it  is  true, 
on  the  flow  of  blood  from  the  great  veins. 

In  the  veins  which  pass  from  above  downwards,  the  force 
of  gravity  favors  the  flow  of  blood.  This  is  seen  by  the  tur- 
gescence  of  the  veins  of  the  neck  and  face,  when  the  head  is 
kept  for  a  short  time  below  the  level  of  the  heart.  If  the 
arm  be  elevated  above  the  head,  the  veins  of  the  back  of  the 
hand  will  be  much  reduced  in  size,  from  the  greater  facility 
with  which  the  blood  passes  to  the  heart ;  while  they  are 


FUNCTION   OF   THE   VALVES.  325 

distended  when  the  hand  is  allowed  to  hang  by  the  side,  and 
the  blood  has  to  mount  up  against  the  force  of  gravity. 

In  the  extreme  irregularity  in  the  rapidity  of  the  circula- 
tion in  different  veins,  it  must  frequently  happen  that  a  ves- 
sel empties  its  blood  into  another  of  larger  size,  in  which  the 
current  is  more  rapid.  In  such  an  instance,  as  a  physical 
necessity,  the  more  rapid  current  in  the  larger  vessel  exerts 
a  certain  suction  force  on  the  fluid  in  the  vessel  which 
joins  with  it. 

Function  of  the  Valves. 

With  our  present  knowledge,  it  is  difficult  to  compre- 
hend how  any  anatomist  could  have  accurately  described 
the  valves  of  the  veins,  and  yet  be  ignorant  of  their  function; 
and  the  fact  that  their  use  was  not  understood  before  the 
description  of  the  circulation  by  Harvey,  shows  the  greatness 
of  this  as  a  discovery,  and  the  shallow  character  of  any  pre- 
tence that  men  of  science  had  any  idea  of  the  motion  of  the 
blood  before  his  time. 

With  our  present  knowledge  of  the  course  of  the  blood, 
it  is  evident  that  the  great  function  of  the  valves  is  in  pre- 
senting an  obstacle  to  the  reflux  of  blood  toward  the  capil- 
lary system ;  and  it  only  remains  to  study  the  conditions 
under  which  they  are  brought  into  action. 

There  are  two  distinct  conditions  under  which  the  valves 
of  the  veins  may  be  closed.  One  of  them  is  the  arrest  of  cir- 
culation, from  any  cause,  in  veins *in  which  the  blood  has  to 
mount  against  the  force  of  gravity  ;  and  the  other,  compres- 
sion of  veins,  from  any  cause  (generally  from  muscular  con- 
traction) which  tends  to  force  the  blood  from  the  vessels 
compressed  into  others,  when  the  valves  offer  an  obstruction 
to  a  flow  toward  the  capillaries,  and  necessitate  a  current  in 
the  direction  of  the  heart. 

In  the  first  of  these  conditions,  the  valves  are  antagonistic 
to  the  force  of  gravity,  and,  when  the  caliber  of  any  vessel  is 


326  CIRCULATION. 

temporarily  obliterated,  aid  in  directing  the  current  into  an- 
astomotic  vessels.  It  is  but  rarely,  however,  that  they  act 
thus  in  opposition  to  the  force  of  gravity ;  and  it  is  only 
when  many  of  the  veins  of  a  part  are  simultaneously  com- 
pressed that  they  aid  in  diverting  the  current.  When  a  sin- 
gle vein  is  obstructed,  it  is  not  probable  that  the  valves  are 
necessary  to  divert  the  current  into  other  vessels,  for  this 
would  take  place  in  obedience  to  the  vis  a  tergo  /  but  when 
many  veins  are  obstructed  in  a  dependent  part,  and  the 
avenues  to  the  heart  become  insufficient,  the  numerous 
valves  divide  the  columns  of  blood,  so  that  the  pressure  is 
equally  distributed  through  the  extent  of  the  vessels.  For  it 
must  be  remembered,  the  strength  of  the  walls  diminishes  as 
we  pass  from  the  larger  veins  to  the  periphery,  and  the  small- 
est vessels,  which,  were  it  not  for  the  valves,  would  be  sub- 
jected to  the  greatest  amount  of  pressure,  are  least  calculated 
to  bear  distention.  This  is  but  an  occasional  function  which 
the  valves  are  called  upon  to  perform  ;  and  it  is  evident  that 
their  influence  is  only  to  prevent  the  weight  of  the  entire 
column  of  blood,  in  vessels  thus  obstructed,  from  operating 
on  the  smallest  veins  and  the  capillaries.  It  cannot  make 
the  labor  of  the  heart,  when  the  blood  is  again  put  in  mo- 
tion, any  less  than  if  the  column  were  undivided,  as  this 
organ  must  have  sufficient  power  to  open  successively  each 
set  of  valves,  when,  of  course,  they  cease  to  have  any  influ- 
ence whatsoever. 

It  is  in  connection  with  the  intermittent  compression  of 
the  veins  that  the  valves  haVe  their  principal  and  almost  con- 
stant function.  Their  situation  alone  would  lead  to  this  sup- 
position. They  are  found  in  greatest  numbers  throughout 
the  muscular  system,  having  been  demonstrated  by  Sappey 
in  the  smallest  venules.  They  are  also  found  in  the  upper 
parts  of  the  body,  where  they  certainly  do  not  operate  against 
the  force  of  gravity,  while  they  do  not  exist  in  the  cavities, 
where  the  venous  trunks  are  not  subject  to  compression.  It 
has  already  been  made  sufficiently  evident  that  the  action  of 


FUNCTION  OF  THE  VALVES.  327 

muscles  seconds  most  powerfully  the  contractions  of  the 
heart.  The  vis  a  tergo  from  the  heart  is,  doubtless,  generally 
sufficient  to  turn  this  influence  of  muscular  compression  from 
the  capillary  system,  and  the  valves  of  the  veins  are  open ; 
but  they  stand  ready,  nevertheless,  to  oppose  any  tendency 
to  regurgitation. 

In  the  action  of  muscles,  the  skin  is  frequently  stretched 
over  the  part,  and  the  cutaneous  veins  are  somewhat  com- 
pressed. This  may  be  seen  in  the  hand,  by  letting  it  hang 
by  the  side  until  the  veins  become  somewhat  swollen,  and 
then  contracting  the  muscles,  when  the  skin  will  become 
tense  and  the  veins  very  much  less  prominent.  Here  the 
valves  have  an  important  action.  The  compression  of  the 
veins  is  much  greater  in  the  substance  of  and  between  the 
muscles  than  in  the  skin ;  but  the  blood  is  forced  from  the 
muscles  into  the  skin,  and  the  valves  act  to  prevent  it  from 
taking  a  retrograde  course.  The  fact  that  the  contraction  of 
muscles  forces  blood  into  the  veins  of  the  skin  may  be  seen 
by  surrounding  the  upper  part  of  the  forearm  with  a  moder- 
ately tight  ligature,  which  will  distend  the  cutaneous  veins 
below.  If  we  now  contract  the  muscles  vigorously,  the  veins 
below  will  become  sensibly  more  distended  and  knotted; 
showing,  at  once,  the  passage  of  blood  into  the  skin,  and  the 
action  of  the  valves. 

When  a  vein  is  distended  by  the  injection  of  air,  or  a 
liquid,  forced  against  the  valves,  it  is  observed  that  at  the 
point  where  the  convex  borders  of  the  valves  are  attached, 
the  vessel  is  not  dilated  as  much  as  at  other  parts.  This  is 
due  to  the  fact  that  the  valves  are  bordered  with  a  fibrous 
ring,  which  strengthens  the  vessel,  and  prevents  distention  at 
that  point,  which  would  separate  the  free  borders  of  the  valves 
and  render  them  insufficient. 

A  full  consideration  of  the  venous  anastomoses  belongs  to 
descriptive  anatomy.  Suffice  it  to  say,  in  this  connection,  that 
they  are  very  numerous,  and  provide  for  a  return  of  the  blood 
to  the  heart  by  a  number  of  channels.  The  azygos  vein,  the 


328  CIRCULATION. 

veins  of  the  spinal  canal,  and  veins  in  the  walls  of  the  abdo- 
men and  thorax,  connect  the  inferior  with  the  superior  vena 
cava«  Even  the  portal  vein  has  lately  been  shown  to  have 
its  communications  with  the  general  venous  system.  Thus, 
in  all  parts  of  the  organism,  temporary  compression  of  a  vein 
only  diverts  the  current  into  some  other  vessel,  and  permanent 
obliteration  of  a  vein  produces  enlargement  of  communicating 
branches,  which  soon  become  sufficient  to  meet  all  the  require- 
ments of  the  circulation. 

Conditions  which  impede  the  Venous  Circulation. 

Influence  of  Expiration. — The  influence  of  expiration  on 
the  circulation  in  the  veins  near  the  thorax,  is  directly  oppo- 
site to  that  of  inspiration.  As  the  act  of  inspiration  has  a 
tendency  to  draw  the  blood  from  these  vessels  into  the  chest, 
the  act  of  expiration  has  a  tendency  to  force  the  blood  out 
from  the  vessels  of  the  thorax,  as  the  air  is  forced  out  by  the 
trachea,  and  opposes  a  flow  in  the  opposite  direction.  The 
effect  of  prolonged  and  violent  expiratory  efforts  is  very 
marked ;  being  followed  by  deep  congestion  of  the  veins  of 
the  face  and  neck,  and  a  sense  of  fulness  in  the  head,  which 
may  become  very  distressing.  The  opposition  to  the  venous 
current  generally  extends  only  to  vessels  in  the  immediate 
vicinity  of  the  thorax,  or,  it  may  be  stated  in  general  terms, 
to  those  veins  in  which  the  flow  of  blood  is  assisted  by  the 
movements  of  inspiration  ;  but,  while  the  inspiratory  influence 
is  absolutely  confined  to  a  very  restricted  circuit  of  vessels, 
the  obstructive  influence  of  very  violent  and  prolonged  expi- 
ration may  be  extended  very  much  further,  as  is  seen  when 
the  vessels  of  the  neck,  face,  and  conjunctiva  become  con- 
gested in  prolonged  vocal  efforts,  blowing,  etc. 

The  mechanism  of  this  is  not  wrhat  we  might  at  first  be 
led  to  suppose  ;  namely,  a  mere  reflux  from  the  large  trunks 
of  the  thoracic  cavity.  "Were  this  the  case,  it  would  be  ne- 
cessary to  assume  an  insufficiency  of  certain  valves,  which 


KEGUKGITANT  VENOUS  PULSE.  329 

does  not  exist.  In  extreme  congestion,  reflux  of  blood  may 
take  place  to  a  certain  extent  in  the  external  jugular,  for  this 
vessel  has  but  two  valves,  which  are  not  competent  to  pre- 
vent regurgitation ; '  but  the  chief  cause  of  congestion  is 
due,  not  to  regurgitation,  but  to  accumulation  from  the  pe- 
riphery, and  an  obstruction  to  the  flow  of  blood  into  the  great 


It  is  in  the  internal  jugular  that  the  influence  of  expiration 
is  most  important,  both  from  the  great  size  of  the  vessel  in  the 
human  subject,  as  compared  with  the  other  vessels,  and  from 
the  importance  and  delicacy  of  the  parts  from  which  it  collects 
the  blood.  At  the  opening  of  this  vessel  into  the  innominate 
vein,  is  a  pair  of  strong  and  perfect  valves,  which  effectually 
close  the  orifice  when  there  is  a  tendency  to  regurgitation. 
These  valves  have  attracted  much  attention  among  physiolo- 
gists, since  the  discovery  of  the  circulation  has  made  it  evi- 
dent how  important  they  might  be  in  protecting  the  brain 
from  reflux  of  blood.  When  the  act  of  expiration  arrests  the 
onward  flow  in  the  veins  near  the  thorax,  these  valves  are 
closed,  and  effectually  protect  the  brain  from  congestion  by 
regurgitation.  The  blood  accumulates  behind  the  valves,  but 
the  free  communication  of  the  internal  jugular  with  the 
other  veins  of  the  neck  relieves  the  brain  from  congestion, 
unless  the  effort  be  extraordinarily  violent  and  prolonged. 

The  above  remarks  with  regard  to  the  influence  of  expira- 
tion are  applicable  to  vocal  efforts,  violent  coughing  or  sneez- 
ing, or  any  violent  muscular  efforts,  such  as  straining,  in 
which  the  glottis  is  closed. 

.Regurgitant  Venous  Pulse. — In  the  inferior  animals,  like 
the  dog,  if  the  external  jugular  be  exposed,  a  distention  of 
the  vessel  is  seen  to  accompany  each  expiratory  act.  This  is 
sometimes  observed  in  the  human  subject,  when  respiration 
is  exaggerated,  and  has  been  called  improperly  the  venous 
pulse.  There  is  no  sufficient  obstacle  to  the  regurgitation  of 

1  GRAY,  Descriptive  Anatomy,  Philadelphia,  1859,  p.  404. 


330  CIRCULATION. 

blood  from  the  thorax  into  the  external  jugular,  and  distinct 
pulsations,  synchronous  with  the  movements  of  respiration, 
may  be  produced  in  this  way. 

In  some  forms  of  cardiac  disease  affecting  the  right  side, 
a  pulsation,  synchronous  with,  the  heart's  action,  has  also 
been  noticed.  This  is  always  confined  to  the  jugular,  and 
must  not  be  connected  with  the  slight  pulsations  which 
sometimes  occur  in  the  veins  of  the  extremities.  It  is  due  to 
a  regurgitant  impulse  from  the  right  side  of  the  heart ;  and 
generally,  to  the  action  of  the  right  ventricle,  propagated  into 
the  veins  on  account  of  pathological  insufficiency  of  the  tri- 
cuspid  valves.  Two  distinct  pulsations  accompanying  each 
act  of  the  heart  have  been  occasionally  observed:  one  im- 
mediately preceding,  and  the  other  coincidiDg  with,  the  ven- 
tricular systole.  In  a  case  of  this  kind,  post-mortem  examin- 
ation revealed  contraction  of  the  right  auriculo-ventricular 
orifice,  as  well  as  insufficiency  of  the  tricuspid  valves.1  The 
relation  of  the  pulsation  of  the  jugular  to  the  action  of  the 
heart  showed  that  the  first  impulse  was  produced  by  the  con- 
traction of  the  right  auricle,  and  the  second  by  the  contrac- 
tion of  the  right  ventricle. 

It  is  evident  that  there  are  various  other  circumstances 
which  may  impede  the  venous  circulation.  Accidental 
compression  may  temporarily  arrest  the  flow  in  any  par- 
ticular vein.  "When  the  whole  volume  of  blood  is  materi- 
ally increased,  as  after  a  full  meal,  with  copious  ingestion  of 
liquids,  the  additional  quantity  of  blood  accumulates  chiefly 
in  the  venous  system,  and  proportionately  diminishes  the  ra- 
pidity of  the  venous  circulation. 

The  force  of  gravity  also  has  an  important  influence.  It 
is  much  more  difficult  for  the  blood  to  mount  from  below  up 
to  the  heart,  than  to  flow  downwards  from  the  head  and 
neck.  The  action  of  this  is  seen  if  comparison  be  made  be- 
tween the  circulation  in  the  arm  elevated  above  the  head 
and  hanging  by  the  side.  In  the  one  case  the  veins  are  read 

1  FLINT,  Diseases  of  the  Heart,  Philadelphia,  1859,  p.  147. 


KEGUKGITANT  VENOUS   PULSE.  331 

ily  emptied,  and  contain  but  little  blood ;  and  in  the  other 
the  circulation  is  more  difficult,  and  the  vessels  are  moderate- 
ly distended.  The  walls  of  the  veins  are  thickest,  and  the 
valves  most  numerous,  in  parts  of  the  body  which  are  habit- 
ually dependent.  The  influence  of  gravity  is  exemplified  in 
the  production  of  varicose  veins  in  the  lower  extremities. 
This  disease  is  frequently  induced  by  occupations  which  re- 
quire constant  standing ;  but  the  exercise  of  walking,  aiding 
the  venous  circulation,  as  it  does,  by  the  muscular  effort,  has 
no  such  tendency. 


CHAPTER  IX. 

PECULIARITIES    OF    THE    CIRCULATION   IN    DIFFERENT    PARTS    OF 
THE   SYSTEM. 

Circulation  in  the  cranial  cavity — Circulation  in  erectile  tissues— Derivative  circu- 
lation— Pulmonary  circulation — General  rapidity  of  the  circulation — Time  re- 
quired for  the  passage  through  the  heart  of  all  the  blood  in  the  organism — 
Relations  of  the  general  rapidity  of  the  circulation  to  the  frequency  of  the 
heart's  action — Phenomena  in  the  circulatory  system  after  death. 

Circulation  in  the  Cranial  Cavity. — In  the  encephalic 
cavity,  there  are  certain  peculiarities  in  the  anatomy  of  some 
of  the  vessels,  with  exceptional  conditions  of  the  blood,  as  re- 
gards atmospheric  pressure,  which  have  been  considered  ca- 
pable of  essentially  modifying  the  circulation.  In  the  adult, 
the  cranium  is  a  closed,  air-tight  box,  containing  the  incom- 
pressible cerebral  substance,  and  blood ;  conditions  which  are 
widely  different  from  those  presented  in  other  parts  of  the 
system.  On  this  account,  some  have  gone  so  far  as  to  con- 
sider any  change  in  the  quantity  of  circulating  fluid  in  the 
brain,  a  physical  impossibility.1  Pathological  facts  in  oppo- 

1  A  number  of  years  ago,  there  was  considerable  interest  excited  in  the  dis- 
cussion of  the  possibility  of  an  increase  or  diminution  in  the  quantity  of  blood  in 
the  brain  under  any  circumstances.  Monro,  Abercrombie,  and  Dr.  Kellie  sup- 
posed the  quantity  of  blood  in  the  brain  to  be  invariable;  Dr.  Kellie  assuming  to 
have  proved  this  position  by  experiments  which  showed  (according  to  his  conclu- 
sions at  least)  no  diminution  in  the  quantity  of  blood  in  the  brain  in  animals 
killed  by  hemorrhage,  and  no  increase  in  the  quantity  in  animals  killed  by  a  liga- 
ture  around  the  neck.  He  made  other  observations  on  this  subject  which  it  is  un- 


CIRCULATION  IN  THE   CRANIUM.  333 

sition  to  such  a  view  are  so  numerous  and  well  established, 
that  the  question  does  not  demand  extended  discussion.  It 
is  well  known,  that  in  certain  cases  the  vessels  of  the  brain 
and  its  membranes  are  found  engorged  with  blood,  and  in 
others  containing  a  comparatively  small  quantity ;  but  it  is 
nevertheless  true  that  there  are  anatomical  peculiarities  in 
these  parts,  the  effects  of  which  on  the  circulation  present 
important  and  interesting  points  for  study. 

In  the  brain,  the  venous  passages  which  correspond  to  the 
great  veins  of  other  parts,  are  sinuses  between  the  folds  of 
the  dura  mater,  and  are  but  slightly  dilatable.  In  the  per- 
fectly consolidated  adult  head,  the  blood  is  not  subjected  to 
atmospheric  pressure  as  in  other  parts,  and  the  semi-solids 
and  liquids  which  compose  the  encephalic  mass  cannot  in- 
crease in  size  in  congestion,  and  dimmish  in  anemia.  Not- 
withstanding these  conditions,  the  undoubted  fact  remains 
that  examinations  of  the  vessels  of  the  brain  after  death  show 
great  differences  in  the  quantity  of  blood  which  they  contain. 
The  question  then  arises  as  to  what  is  displaced  to  make 
room  for  the  blood  in  congestion,  and  what  supplies  the 
place  of  the  blood  in  anemia. 

An  anatomical  peculiarity,  which  has  not  yet  been  con- 
sidered, offers  an  explanation  of  these  phenomena.  Magen- 
die  has  shown  by  observations  on  living  animals,  confirmed 
by  dissections  of  the  human  body,  that  between  the  pia  mater 
and  the  arachnoid  of  the  brain  and  spinal  cord  there  exists  a 


necessary  to  enumerate.  These  experiments  were  fully  reviewed  by  Dr.  George 
Burrows,  who  shows  by  his  quotations  from  Dr.  Kellie  that  they  proved  nothing 
of  the  kind.  Dr.  B.  repeated  the  experiments  on  rabbits,  and  demonstrated  that 
great  variations  exist  in  the  quantity  of  blood  in  the  brain,  when  the  animals  are 
killed  in  different  ways.  He  showed  that  the  blood-vessels  are  engorged  when  the 
head  is  left  dependent  for  a  number  of  hours,  and  that  they  contain  but  little 
blood  when  it  is  elevated.  Certain  of  Kellie's  experiments,  cited  by  Dr.  Burrows, 
show  that  the  difference  is  in  the  conclusions,  and  not  in  the  experimental 
facts.  For  a  full  discussion  of  this  subject,  the  reader  is  referred  to  the  work 
of  Dr.  Burrows  on  Disorders  of  the  Cerebral  Circulation,  &c.  (American  reprint), 
Philadelphia,  1848. 


334  CIRCULATION. 

liquid,  the  cephalo-rachidian  fluid,  which  is  capable  of  pass- 
ing from  the  surface  of  the  brain  to  the  spinal  canal,  and 
communicates  with  the  fluid  in  the  ventricles.1  This  he  has 
conclusively  demonstrated  to  be  situated,  not  between  the 
layers  of  the  arachnoid,  as  was  supposed  by  Bichat,  but  be- 
tween the  inner  layer  of  this  membrane  and  the  pia  mater. 
The  communication  between  the  cranial  cavity  and  frhe  spinal 
canal  is  very  free.  This  was  demonstrated  by  exposing  the 
dura  mater  of  the  brain  and  of  the  cord,  making  an  opening 
in  the  membranes  of  the  cord,  so  as  to  allow  the  liquid  to 
escape  (which  it  does  in  quite  a  forcible  jet),  when  pressure 
on  the  membranes  of  the  brain  not  only  accelerated  the  flow, 
but  pressed  out  a  quantity  of  the  liquid  after  all  that  would 
escape  spontaneously  had  been  evacuated. 

It  is  easy  to  see  one  of  the  physiological  uses  of  this  liquid. 
When  the  pressure  of  blood  in  the  arteries  leading  to  the 
brain  is  increased,  or  when  there  is  an  obstacle  to  its  return 
by  the  veins,  more  or  less  congestion  takes  place,  and  the 
blood  forces  the  liquid  from  the  cranial  into  the  spinal  cavity ; 
the  reverse  taking  place  when  the  supply  of  blood  to  the  brain 
is  diminished.  The  functions  of  all  highly  organized  and 
vascular  parts  seem  to  require  certain  variations  in  the  sup- 
ply of  blood ;  and  there  is  no  reason  to  suppose  that  the 
brain,  in  its  varied  conditions  of  activity  and  repose,  is  any 
exception  to  this  general  rule,  though  the  physiological  con- 
ditions of  its  vascularity  are  not  easily  studied. 

In  some  late  experiments  by  Mr.  Durham  on  the  physi- 
ology of  sleep,  the  comparative  vascularity  of  the  meninges 
of  the  brain  at  different  times  has  been  studied  in  animals,  by 
removing  a  portion  of  the  skull  with  a  trephine,  and  supply- 
ing its  place  by  a  watch-glass  cemented  to  the  edges  of  the 
bone  with  Canada  balsam.  In  these  experiments,  the  author 
demonstrates  that  the  vessels  are  much  more  congested  dur- 

1  MAGENDIE,  Journal  de  Physiologic,  1825,  tome  v.,  p.  27  et  seg.,  and  1827, 
tome  vii.,  p.  66  et  seq.  Sur  un  Liquide  gut  se  trouve  dans  le  Crane  et  le  Canal 
Vertibral  de  VHomme  et  des  Animaux  Mammiferes. 


CIRCULATION   IN  THE   CRANIUM.  335 

ing  the  activity  of  the  brain,  than  during  the  suspension  of 
its  functions  in  sleep.  The  blood-vessels  of  the  meninges 
were  exposed  freely  to  view  by  the  operation,  and  were  ex- 
amined by  the  microscope,  with  a  low  power,  as  well  as  with 
the  naked  eye.1  Dr.  Hammond  has  lately  published  an  in- 
teresting paper  on  sleep  and  insomnia,  in  which  the  obser- 
vations of  Mr.  Durham  are  fully  confirmed,  leaving  no  doubt 
that  the  vessels  within  the  cranial  cavity  are  subject  to  con- 
siderable physiological  variations  in  tension.  These  obser- 
vations were  published  in  1865,2  though  they  were  made 
before  the  article  of  Mr.  Durham  appeared. 

Physiologists,  even  before  the  time  of  Haller,  had  noticed 
alternate  movements  of  expansion  and  contraction  in  the 
brain,  connected  with  the  acts  of  respiration.  'This  is  ob- 
served in  children  before  the  fontanels  are  closed,  and  in 
the  adult  when  the  brain  is  exposed  by  an  injury  or  a 
surgical  operation.  The  movements  are,  an  expansion  with 
the  act  of  expiration,  which,  in  violent  efforts,  is  sometimes 
so  considerable  as  to  produce  protrusion,  and  contraction 
with  inspiration.  Magendie  also  studied  these  movements, 
which  he  explained  in  the  following  way  : 3  With  the  act  of 
expiration,  the  flow  of  blood  in  the  arteries  is  favored,  and 
the  current  in  the  veins  is  retarded.  If  the  effort  be  violent, 
the  valve  at  the  opening  of  the  internal  jugular  may  be 
closed.  This  act  would  produce  an  expansion  of  the  brain, 
not  from  reflux  by  the  veins,  but  from  the  fact  that  the  flow 
into  the  chest  is  impeded,  and  the  blood,  while  passing  in 
more  freely  by  the  arteries,  is  momentarily  confined.  With 
inspiration,  the  flow  into  the  thorax  is  materially  aided,  and 
the  brain  is  in  some  degree  relieved  of  this  expanding  force. 


1  ARTHUR  E.  DURHAM,  The  Physiology  of  Sleep.    Guy's  Hospital  Reports,  1860, 
p.  149. 

2  War.  A.  HAMMOMD,  M.D.,  On  Sleep  and  Insomnia.     New  York  Medical  Jour- 
nal, 1865,  vol.  i.,  Nos.  2  and  3. 

8  Journal  de  Physiologic,  tome  i.,  p.  132.  De  F  Influence  des  Mouvements  de  la 
Poitrine  et  des  Efforts  sur  la  Circulation  du  Sang. 


336  CIRCULATION. 

Kobin  has  lately  noted  a  peculiarity  in  the  small  vessels 
of  the  brain,  spinal  cord,  and  pia  mater,  which  is  curious,  but 
the  physiological  function  of  which  is  not  yet  apparent.1 
These  vessels  are  surrounded  by  a  thin,  amorphous  sheath, 
which  has  a  diameter  of  from  j-^j-  to  -^^  of  an  inch  greater 
than  that  of  the  vessel  itself.  Between  this  and  the  blood- 
vessel is  a  transparent  liquid.  This  structure,  which  has 
been  observed  in  no  other  part  of  the  circulatory  system,  is 
regarded  by  its  discoverer  as  the  commencement  of  the  lym- 
phatics of  the  nervous  centres.  What  effect  this  disposition 
of  the  vessels  may  have  upon  the  facility  with  which  they 
may  become  dilated  or  contracted,  it  is  difficult  to  determine. 

Circulation  in  Erectile  Tissues. — In  the  organs  of  gener- 
ation in  both  sexes  there  exists  a  tissue  which  is  subject  to 
great  increase  in  volume  and  rigidity,  when  in  a  state  of  what 
is  called  erection.  The  parts  in  which  the  erectile  tissue  ex- 
ists are,  in  the  male,  the  corpora  cavernosa  of  the  penis,  the 
corpora  spongiosa,  with  the  glans  penis ;  and  in  the  female, 
the  corpora  cavernosa  of  the  clitoris,  the  gland  of  the  clitoris, 
and  the  bulb  of  the  vestibule.  In  addition,  Kouget  has  lately 
demonstrated  the  presence  of  true  erectile  tissue  in  the  body 
of  the  uterus,  and  in  a  bulb  annexed  to  the  ovary  of  the  hu- 
man female,  but  states  that  it  is  not  found  in  the  inferior 
animals.  He  has  shown  by  injections  that  the  uterus  is 
capable  of  erection  like  the  penis.2  In  some  other  parts, 
such  as  the  nipple  and  the  mucous  membrane  of  the 
vagina,  which  are  sometimes  described  as  erectile,  the  pecu- 
liar vascular  arrangement  which  is  characteristic  of  true 
erectile  tissues  is  not  found.  In  the  nipple,  the  hardness 
which  follows  gentle  stimulation  is  simply  the  result  of  con- 
traction of  the  smooth  muscular  fibres  with  which  this  part 

1  ROBIN,  Sur  une  Tunigue  Appartenante  cnpropre  aux  Capillaires  Encephalo- 
Rachidiens.  Journal  de  la  Physiologic,  etc.,  Oct.  1859,  tome  ii.,  p.  543. 

3  ROUGET,  JRecherches  sur  les  Organes  Erectiles  de  la  Femme,  etc.  Journal 
de  la  Physiologic,  Paris,  1858,  tome  L,  pp.  320,  479,  735. 


ERECTILE   TISSUES.  337 

is  largely  supplied,  and  is  analogous  to  the  elevations  in  the 
follicles  of  the  skin  from  the  same  cause,  in  what  is  called 
goose-flesh.  In  the  vagina,  congestion  may  occur,  as  in  other 
mucous  membranes,  but  there  is  no  proper  erection. 

The  vascular  arrangement  in  erectile  organs,  of  which  the 
penis  may  be  taken  as  the  type,  is  peculiar  to  them,  and  not 
found  in  any  other  part  of  the  circulatory  system.  Taking 
the  penis  as  an  example,  the  arteries,  which  have  an  unusually 
thick  muscular  coat,  after  they  have  entered  the  organ,  do  not 
simply  branch  and  divide  dichotomously,  as  in  most  other 
parts,  but  send  off  large  numbers  of  arborescent  branches, 
which  immediately  become  tortuous,  and  are  distributed  in 
the  cavernous  and  spongy  bodies  in  numerous  anastomosing 
vessels,  with  but  a  single  thin  homogeneous  coat,  like  the  true 
capillaries.  These  vessels  are  larger,  even,  than  the  arterioles 
which  supply  them  with  blood,  some  having  a  diameter 
of  from  -^  to  ^  of  an  inch.1  The  cavernous  bodies  have  an 
external  investment  of  strong  fibrous  tissue  of  considerable 
elasticity,  which  sends  bands,  or  trabeculse,  into  the  interior, 
by  which  it  is  divided  up  into  cells.  The  trabeculse  are  com- 
posed of  fibrous  tissue  mixed  with  a  large  number  of  smooth 
muscular  fibres.  These  cells  lodge  the  blood-vessels,  which 
ramify  in  the  tortuous  manner  already  indicated,  and  finally 
terminate  in  the  veins.2  The  anatomy  of  the  corpora  spon- 
giosa  is  essentially  the  same ;  the  only  difference  being  that 
the  fibrous  envelope  and  the  trabeculse  are  more  delicate, 
and  the  cells  are  of  smaller  size. 

Without  going  fully  into  the  mechanism  of  erection, 
which  comes  more  properly  under  the  head  of  generation,  it 
may  be  stated  in  general  terms  that  during  sexual  excite- 

1  ROBIN,  Observations  sur  la  Constitution  du  Tissu  Erectile,  Paris,  1865. 

2  J.  Miiller  professed  to  have  discovered  a  peculiarity  in  the  arteries  of  erectile 
tissues  consisting  in  arborescent  diverticula  from  the  main  vessel,  with  blind  ex- 
tremities.    These  he  called  the  helicine  arteries.     (Manuel  de  Physiologic.    Trad. 
parJourdan,  Paris,  1851,  tome  i.,  p.  181.)    Rouget  in  his  admirable  article  (loc. 
cit.)  has  gone  over  the  experiments  of  Miiller,  and  shown  conclusively  that  the 
so-called  helicine  arteries  do  not  exist ;  and  that  the  appearances  described  by 
Miiller  are  due  to  imperfect  filling  of  the  vessels  by  the  injection. 

22 


338  CIRCULATION. 

ment,  or  when  erection  occurs  from  any  cause,  the  thick  mus- 
cular walls  of  the  arteries  of  supply  relax,  and  allow  the  ar- 
terial pressure  to  distend  the  capacious  vessels  lodged  in  the 
cells  of  the  cavernous  and  spongy  bodies.  This  produces  the 
characteristic  change  in  the  volume  and  position  of  the  organ. 
It  is  evident  that  erection  depends  upon  the  peculiar  arrange- 
ment of  the  blood-vessels,  and  is  not  simply  a  congestion, 
such  as  could  occur  in  any  vascular  part.  During  erection, 
there  is  not  a  stasis  of  blood  ;  but  if  it  continue  for  any  length 
of  time,  the  quantity  which  passes  out  of  the  part  by  the 
veins  must  be  equal  to  that  which  passes  in  by  the  arteries. 
If  return  by  the  veins  were  prevented,  gangrene  would  inev- 
itably supervene,  an  occurrence  which  sometimes  takes  place 
when  the  root  of  the  penis  has  become  constricted,  and  is  not 
speedily  relieved.  Erection  may  be  produced  in  the  dead 
body,  by  preventing  reflux  by  the  veins,  and  filling  the  ves- 
sels contained  in  the  cells  of  the  cavernous  and  spongy  bodies 
by  injection.  It  has  been  shown  by  Miiller  that  the  penis 
may  be  made  rigid  by  an  injection  at  a  pressure  about  equal 
to  the  pressure  of  blood  in  the  arteries.1 

The  mechanism  of  erection  of  the  clitoris,  and  other 
erectile  parts,  is  essentially  the  same  as  in  the  penis.  It  is 
seen  that  in  this  condition,  circulation  is  by  no  means  arrested ; 
and  the  tortuous  vessels  are  filled  with  blood  by  an  enlarge- 
ment in  the  caliber  of  the  small  arteries  of  supply. 

Ronget  has  shown  that  the  body  of  the  uterus  possesses  an 
erectile  tissue  as  perfect  as  that  of  the  penis ;  and  that  after 
death  the  organ  may  be  made  to  change  its  form  and  posi 
tion  by  injecting  the  vessels,  when  it  increases  in  size  about 
one-half,  rising  up,  and  becoming  rigid  and  erect  in  the  cavity 
of  the  pelvis.2 

This  relaxation  of  the  muscular  coats  of  the  arteries  only 
exists  for  a  time;  tonic  contraction  occurs,  the  supply  of 
blood  is  diminished,  and  the  organ  returns  to  its  ordinary 
condition. 

1  J.  MULLER,  op.  cit.,  tome  i.,  p.  182.  2  ROUGET,  op.  cit.,  pp.  338,  339. 


DERIVATIVE  CIRCULATION.  330 

Under  stimulation,  the  muscular  fibres  in  the  covering 
and  trabeculse  of  the  corpora  cavernosa  and  spongiosa  may 
contract,  force  the  blood  from  the  parts,  and  produce  a  cer- 
tain amount  of  rigidity,  with  diminution  in  size.  This  is 
frequently  seen  under  the  influence  of  cold,  which  is  a  pow- 
erful excitant  of  the  unstriped  muscular  fibres. 

Derivative  Circulation. — In  some  parts  of  the  circulatory 
system,  there  exists  a  direct  communication  between  the  arte- 
ries and  the  veins,  so  that  all  the  blood  does  not  necessarily 
pass  through  the  minute  vessels  which  have  been  described 
as  true  capillaries.  This  peculiarity  has  been  closely  studied 
by  M.Sucquet,who  was  first  led  to  investigate  the  subject  by 
noticing  that  by  injecting  a  very  small  quantity  of  fluid,  en- 
tirely insufficient  to  fill  all  the  capillaries  of  a  member,  it  was 
returned  by  certain  of  the  veins.  On  using  a  black,  solidifi- 
able  injection,  he  found  that  there  were  certain  parts  of  the 
upper  and  lower  extremities  and  the  head  which  became 
colored  by  the  injection,  while  other  parts  were  not  pene- 
trated. Following  this  out  by  dissection,  he  showed  that,  in 
the  upper  extremity,  the  skin  of  the  fingers  and  part  of  the 
palm  of  the  hand,  and  the  skin  over  the  olecranon,  is  provided 
with  vessels  of  considerable  size,  which  allowed  the  fluid  in- 
jected by  the  axillary  artery  to  pass  directly  into  some  of 
the  veins,  while  in  other  parts  the  veins  were  entirely  empty. 
Extending  his  researches  to  the  lower  extremity,  he  found 
analogous  communications  between  the  vessels  in  the  knee, 
toes,  and  parts  of  the  sole  of  the  foot.  He  also  found  com- 
munications in  the  nose,  cheeks,  lips,  forehead,  and  ends  of 
the  ears,  parts  which  are  particularly  liable  to  changes  in  color 
from  congestion  of  vessels.1 

1  J.  P.  SUCQUET,  De  la  Circulation  du  Sang  dans  les  Membres  et  dans  la  Tete 
de  rilomme,  Paris,  1860,  p.  55.  Though  all  the  physiological  deductions  in  this 
memoir  do  not  seem  justifiable,  the  anatomical  facts  are  undoubted.  The  prepa- 
rations have  been  examined  by  a  commission,  of  which  M.  Robin  was  a  member, 
which  confirmed  the  statements  of  M.  Sucquet.  (Oral  communication  from  M. 
Robin.) 


34:0  CIRCULATION. 

It  is  evident  that,  under  certain  circumstances,  a  larger 
quantity  of  blood  than  usual  may  pass  through  these  parts 
without  necessarily  penetrating  the  true  capillaries  and  thus 
exerting  a  modifying  influence  upon  nutrition.  The  changes 
which  are  liable  to  occur  in*  the  quantity  of  blood,  in  the 
force  of  the  heart's  action,  etc.,  may  thus  take  place  without 
disturbing  the  circulation  in  the  capillaries,  a  provision  which 
the  functions  of  the  parts  would  seem  to  demand.1 

Pulmonary  Circulation. — The  vascular  system  of  the 
lungs  merits  the  name,  which  is  frequently  applied  to  it,  of 
the  lesser  circulation.  The  right  side  of  the  heart  acts  simul- 
taneously with  the  left,  but  is  entirely  distinct  from  it,  and  its 
muscular  walls  are  very  much  less  powerful.  The  pulmo- 
nary artery  has  thinner  and  more  distensible  coats  than  the 
aorta,  and  distributes  its  blood  to  a  single  system  of  capil- 
laries, which  are  located  very  near  the  heart.  We  have  seen 
that  the  orifice  of  the  pulmonary  artery  is  provided  with 
valves  which  prevent  regurgitation  into  the  ventricle.  In 
the  substance  of  the  lungs,  the  pulmonary  artery  is  broken 
up  into  capillaries,  most  of  them  just  large  enough  to  allow 
the  passage  of  the  blood-corpuscles  in  a  single  row.  These 
vessels  are  provided  with  a  single  coat,  and  form  a  very  close 
network  surrounding  the  air-cells.  From  the  capillaries,  the 
blood  is  collected  by  the  pulmonary  veins,  and  conveyed  to 

1  Before  the  publication  of  the  researches  of  Suquet,  Todd  and  Bowman  men- 
tioned the  possibility  of  direct  communications  between  the  arteries  and  veins  in 
many  parts  of  the  body,  and  the  probable  existence  of  such  communications  in 
some  of  the  bones. 

"It  is  not  improbable  that  further  research  may  detect  a  direct  communication 
between  arteries  and  veins,  even  in  tissues,  the  greatest  part  of  which  is  furnished 
with  a  true  capillary  plexus.  In  the  cancellated  structure  of  bone,  and  the  diploe 
of  the  cranial  bones,  it  seems  highly  probable  that  the  arteries  communicate  im- 
mediately with  the  veins  at  many  points.  Mr.  Paget  (Lectures  on  Inflammation) 
describes  a  direct  communication  between  the  arteries  and  veins  of  the  wing  of 
the  bat,  without  any  intermediate  capillary  plexus." — TODD  and  BOWMAN,  Physi- 
ological Anatomy  and  Physiology  of  Man,  American  edition,  Philadelphia,  1857, 
p.  662. 


PULMONARY  CIRCULATION.  34:1 

the  left  auricle.  There  is  no  great  disparity  between  the  ar- 
teries and  veins  of  the  pulmonary  system  as  regards  capacity. 
The  pulmonary  veins  in  the  human  subject  are  not  provided 
with  valves. 

The  blood  in  its  passage  through  the  lungs  does  not  meet 
with  the  resistance  which  is  presented  in  the  systemic  circu- 
lation. This  fact  we  have  often  noticed  in  injecting  defibrin- 
ated  blood  through  the  lungs  of  an  animal  just  killed.  We 
have  also  observed  that  an  injection  passes  through  the  lungs 
as  easily  when  they  are  collapsed  as  when  they  are  inflated. 
The  anatomy  of  the  circulatory  system  in  the  lungs  and  of 
the  right  side  of  the  heart  shows  that  the  blood  must  pass 
through  these  organs  with  comparative  ease.  The  power  of 
the  right  ventricle  is  evidently  less  than  half  that  of  the  left, 
and  the  pulmonary  artery  will  sustain  a  much  less  pressure 
than  the  aorta. 

The  two  sides  of  the  heart  act  simultaneously ;  and  while 
the  blood  is  sent  by  the  left  ventricle  to  the  system,  it  is  sent 
by  the  right  ventricle  to  the  lungs.  Some  physiologists  have 
endeavored  to  measure  the  pressure  of  blood  in  the  pulmo- 
nary artery.  The  only  experiments  which  have  not  involved 
opening  the  thoracic  cavity,  wan  operation  which  must  inter- 
fere materially  with  the  pressure  of  blood  in  the  pulmonary 
artery,  as  it  does  with  the  general  arterial  pressure,  are  those 
of  Chauveau  and  Faivre.1  These  observers  measured  the 
pressure  by  connecting  a  cardiometer  with  a  trocar  intro- 
duced into  the  pulmonary  artery  of  a  living  horse,  through 
one  of  the  intercostal  spaces,  and  found  it  to  be  about  one- 
third  as  great  as  the  pressure  in  the  aorta ;  an  estimate  which 
corresponds  pretty  nearly  with  the  comparative  power  of  the 
two  ventricles,  as  deduced  from  the  thickness  of  their  muscu- 
lar walls. 

Anatomy  teaches  us  that  the  capillaries  of  the  lungs  have 
exceedingly  delicate  walls ;  and  it  is  evident  that  rupture  of 
these  vessels  from  excessive  action  of  the  heart  would  lead  to 

1  LONGET,  Traite  de  Physiologic,  Paris,  1861,  tome  i.,  pp.  886,  887. 


34:2  CIRCULATION. 

grave  results.  It  has  already  been  noted  that  on  the  right 
side  the  lungs  are  protected  bj  an  insufficiency  of  the  auri- 
culo-ventricular  valves,  which  does  not  exist  on  the  left  side, 
allowing  of  a  certain  degree  of  regurgitation  when  the  heart 
is  acting  with  unusual  force,  and  thus  relieving,  to  a  certain 
extent,  the  pulmonary  system.  This  was  pointed  out  by  Mr. 
King  of  London,  and  called  the  safety-valve  function  of  the 
right  ventricle.1  We  have  noticed,  in  the  heart  of  the  ox,  a  like 
disparity  between  the  aortic  and  pulmonic  semilunar  valves. 
If  these  be  exposed  on  both  sides  by  cutting  away  portions  of 
the  ventricles,  and  a  current  of  liquid  be  forced  against  them 
through  the  vessels,  the  aortic  valves  will  be  found  to  entire- 
ly prevent  the  passage  of  the  liquid,  even  under  very  great 
pressure,  while  the  pulmonic  valves  permit  regurgitation  un- 
der a  very  inconsiderable  pressure.  A  little  reflection  will 
make  it  evident  that  when  the  heart  is  acting  with  undue 
force  it  is  quite  as  important  to  relieve  the  lungs  by  a  certain 
amount  of  regurgitation  from  the  pulmonary  artery,  as  by 
insufficiency  of  the  tricuspid  valves.  This  insufficiency  is 
important,  both  at  the  auriculo-ventricular  and  pulmonic  ori- 
fices, in  protecting  the  delicate  structure  of  the  lungs  from 
the  variations  in  force  to  which  the  action  of  both  ventricles 
is  constantly  liable. 

On  microscopic  examination  of  the  circulation  in  the 
lower  animals,  as  the  frog,  the  movement  of  blood  in  the  ca- 
pillaries of  the  lungs  does  not  present  any  differences  from  the 
capillary  circulation  in  other  parts ;  except  that  the  vessels 
seem  more  crowded  with  corpuscles,  and  there  is  no  "  still 
layer  "  next  their  walls. 

There  are  no  forces  of  any  moment  which  are  superadded 
to  the  action  of  the  right  ventricle,  in  the  production  of  the 
arterial,  capillary,  or  venous  circulation  in  the  lungs;  but 
there  are  certain  conditions  which  may  obstruct  the  flow  of 
blood  through  these  parts.  We  have  already  noted  the  effect 
of  introduction  of  air  into  the  veins,  in  blocking  up  the  capil- 

4  Guy's  Hospital  Reports,  1837. 


GENERAL   RAPIDITY.  343 

laries  of  the  lungs,  and  preventing  the  passage  of  blood.  It 
is  a  view  pretty  generally  entertained,  that  in  asphyxia  the 
non-aeration  of  the  blood  obstructs  the  pulmonary  circula- 
tion. We  have  already  considered  this  subject  rather  fully 
in  treating  of  the  general  effects  of  arrest  of  respiration  on 
the  circulation.  The  celebrated  experiments  of  Bichat  dem- 
onstrated the  passage  of  black  blood  through  the  lungs  in  as- 
phyxia, and  its  presence  in  the  arterial  system.  The  experi- 
ments of  Dalton  and  others  have  shown  that  in  this  condi- 
tion, the  obstruction  to  the  circulation  occurs  first  in  the  sys- 
temic capillaries,  and  the  distention  is  propagated  backward 
through  the  great  vessels  and  left  cavities  of  the  heart  to  the 
right  side.  When  the  heart  is  exposed  in  a  living  animal, 
and  artificial  respiration  is  kept  up,  arrest  of  respiration 
produces  engorgement  and  labored  action  of  both  sides. 
There  are  no  observations  which  show  that  increase  of  press- 
ure in  the  pulmonary  artery  is  the  first  and  immediate  result 
of  asphyxia.  It  is  true,  that  after  death  the  right  side  of  the 
heart  is  engorged ;  but  it  is  well  known,  from  observations 
after  death,  and  experiments  on  living  animals,1  that  the 
tonic  contraction  of  the  arteries  is  competent  to  empty  the 
blood  into  the  veins ;  and  the  facts  just  stated  regarding  the 
insufficiency  of  the  pulmonic  semilunar  valves  explain  how 
the  right  side  of  the  heart  may  become  engorged  as  the  result 
of  obstruction  to  the  blood-current  in  the  left  side.  Estab- 
lished facts  seem  to  show  that  asphyxia  does  not  ^primarily 
affect  the  pulmonary  circulation ;  but  that  it  is  possible  for 
venous  blood  to  pass  through  the  lungs  without  undergoing 
arterialization. 

General  Rapidity  of  the  Circulation. 

Several  questions  of  considerable  physiological  interest 

arise  in  connection  with  the  general  rapidity  of  the  circulation : 

1.  It  would  be  interesting  to  determine,  if  possible,  what 

1  See  experiments  by  MAGENDIE  on  the  causes  of  the  circulation  in  the  veins. 
Precis  fiUmenlaire  de  Physiologic,  Paris,  1833,  tome  ii.,  p.  391. 


344  CIRCULATION. 

length  of  time  is  occupied  by  the  blood  in  its  passage 
through  the  entire  circuit  of  both  the  lesser  and  greater 
circulations. 

2.  What  is  the  time  required  for  the  passage  of  the  entire 
mass  of  blood  through  the  heart  ? 

3.  "What  influence  has  the  number  of  pulsations  of  the 
heart  on  the  general  rapidity  of  the  circulation  ? 

The  first  of  these  questions  is  the  one  which  has  been 
most  satisfactorily  answered  by  experiments  on  living  ani- 
mals. In  1827,  Hering,1  a  German  physiologist,  performed 
the  experiment  of  injecting  into  the  jugular  vein  of  a  living 
animal  a  harmless  substance,  which  could  be  easily  recog- 
nized by  its  chemical  reactions,  and  noted  the  time  which 
elapsed  before  it  could  be  detected  in  the  blood  of  the  vein  of 
the  opposite  side.  This  gave  the  first  correct  idea  of  the  rapid- 
ity of  the  circulation ;  for  though  the  older  physiologists,  such 
as  Haller,  Hales,  and  Keill,  had  studied  the  subject,  their  esti- 
mates were  founded  on  calculations  which  had  no  accurate 
basis,  and  gave  very  different  results.  The  experiment  of 
Hering  is  often  roughly  performed  as  a  physiological  demon- 
stration ;  and  we  have  thus  had  frequent  occasions  to  verify, 
in  a  general  way,  its  accuracy.  If,  for  example,  we  expose 
both  jugulars  of  a  dog,  inject  into  one  a  solution  of  ferro-cy- 
anide  of  potassium  in  water,  and  draw  a  specimen  of  blood 
from  the  other  with  as  little  loss  of  time  as  possible,  it  will 
be  found,  that  in  twenty  or  thirty  seconds  after  the  injection, 
the  salt  has  had  time  to  pass  from  the  jugular  to  the  right 
heart,  thence  to  the  lungs  and  left  heart,  from  this  through 
the  capillaries  of  the  head  and  face  back  to  the  jugular  on 
the  opposite  side.  Its  presence  can  be  determined  by  the 
distinct  blue  color  produced  on  the  addition  of  the  perchlo- 
ride  of  iron  to  the  serum,  if  the  specimen  be  allowed  to 
stand,  or  a  clear  extract  of  the  blood  may  be  made  by  boiling 
with  a  little  sulphate  of  soda  and  filtering,  treating  the  color- 
less liquid  thus  obtained  with  the  salt  of  iron. 

1  MILNE-EDWARDS,  Lemons  sur  la  Physiologie,  tome  iv.,  p.  362,  note, 


GENERAL  BAPEDITY.  345 

The  experiments  of  Hering  were  evidently  conducted  with 
great  care  and  accuracy.  He  drew  the  blood  at  intervals  of 
five  seconds  after  the  commencement  of  the  injection,  and 
thus,  by  repeated  observations,  ascertained  pretty  nearly  the 
rapidity  of  a  circuit  of  blood  in  the  animals  on  which  he  ex- 
perimented. Others  have  taken  up  these  investigations,  and 
introduced  some  modifications  in  the  manipulations.  Yier- 
ordt  collected  the  blood  as  it  flowed,  in  little  vessels  fixed  on 
a  disk  revolving  at  a  known  rate,  which  gave  a  little  more 
exactness  to  the  observations ;  *  but  the  method  is  essentially 
the  same  as  that  employed  by  Hering,  and  the  results  obtain- 
ed by  these  two  observers  nearly  correspond. 

The  length  of  time  occupied  by  a  portion  of  blood  in 
making  a  complete  circuit  of  the  vascular  system,  in  the  hu- 
man subject,  is  only  to  be  deduced  from  observations  on  the 
inferior  animals  ;  but  before  this  application  is  made,  it  will 
be  well  to  examine  the  objections,  if  any  exist,  to  the  experi- 
mental procedure  above  described. 

The  only  objection  which  could  be  made  is,  that  a  saline 
solution,  introduced  into  the  torrent  of  the  circulation,  would 
have  a  tendency  to  diffuse  itself  throughout  the  whole  mass 
of  blood,  it  might  be,  with  considerable  rapidity ;  and  that 
this  fact  is  opposed  to  the  proposition  that  the  salt,  when  de- 
tected in  a  specimen  of  blood  drawn  from  a  given  vessel,  is 
simply  carried  there  by  the  force  of  the  blood-current.  This 
objection  to  the  observations  of  Hering  has  been  made  by 
Matteucci,  and  is  considered  by  him  as  fatal  to  their  accu- 
racy.5 It  certainly  is  an  element  which  should  be  taken  into 
account;  but  from  the  definite  data  which  have  been  ob- 
tained concerning  the  rapidity  of  the  arterial  circulation,  and 
the  inferences  which  are  unavoidable  with  regard  to  the  ra- 
pidity of  the  venous  circulation,  it  would  seem  that  the  saline 
solution  must  be  carried  on  by  the  mere  rapidity  of  the  arte- 
rial flow  to  the  capillaries,  which  are  very  short,  taken  up 

1  MILNE-EDWARDS,  loc.  cit. 

3  MATTEUCCI,  Phenomenes  Physiques  dcs  Corps  Vivants,  p.  326  et  scq. 


346  CIRCULATION. 

from  them,  and  carried  on  by  the  veins,  and  thus  through  the 
entire  circuit,  l>efore  it  has  had  time  to  diffuse  itself  suffi- 
ciently to  interfere  with  the  observation.  It  is  not  apparent 
how  this  objection  can  be  overcome,  for  a  substance  must  be 
used  which  will  mix  with  the  blood,  otherwise  it  could  not 
pass  through  the  capillaries.  The  objection  made  by  Mat- 
teucci,  especially  as  it  does  not  appear  how  the  difficulty  can 
be  obviated,  seems  an  unnecessary  refinement ;  for  the  ques- 
tion itself  is  not  one  of  vital  importance,  on  which  depends 
an  important  physiological  principle,  but  simply  one  to 
which  a  tolerably  close  approximation  of  the  exact  truth  is  a 
sufficient  answer.  It  is  interesting  to  know  that  the  varied 
and  complicated  actions  which  we  have  been  studying  effect 
a  single  complete  circuit  of  the.  blood  in  about  half  a  min- 
ute ;  but  it  makes  no  great  difference  whether  it  be  four  or 
five  seconds  more  or  less.  In  this  statement,  we  must  not  be 
understood  as  denying  the  value  of  the  closest  possible  accu- 
racy in  physiological  investigations ;  but  it  is  evident  that 
this  accuracy  is  important  in  proportion  to  the  importance 
of  the  question,  in  itself,  and  in  its  physiological  relations. 

There  seems  no  reason  why,  with  the  above  restrictions, 
the  results  obtained  by  Hering  should  not  be  accepted,  and 
their  application,  as  far  as  possible,  made  to  the  human 
subject. 

Hering  found  that  the  rapidity  of  the  circulation  in  dif- 
ferent animals  was  in  inverse  ratio  to  their  size,  and  in  direct 
ratio  to  the  rapidity  of  the  action  of  the  heart. 

The  following  are  the  mean  results  in  certain  of  the  do- 
mestic animals,  taking  the  course  from  jugular  to  jugular, 
when  the  blood  passes  through  the  lungs  and  through  the 
capillaries  of  the  face  and  head : 

In  the  Horse,  the  circulation  is  accomplished  in  27'3  seconds. 
"     Dog,  "  "  16-2      " 

"     Goat,  "  «  12-8      " 

"     Rabbit,  "  "  6-9       "' 

1  MILNE-EDWARDS,  loc.  cit.    Vierordt  found  the  mean  rapidity  in  the  horse 


GENERAL  RAPIDITY.  347 

Applying  these  results  to  the  human  subject,  taking 
into  account  the  size  of  the  body  and  the  rapidity  of  the 
heart's  action,  the  duration  of  the  circuit  from  one  jugular 
to  the  other  is  estimated  at  21*4  seconds,  and  the  general 
average  through  the  entire  system,  at  23  seconds.  This  is 
simply  approximative ;  but  the  results  in  the  inferior  ani- 
mals may  be  received  as  very  nearly,  if  not  entirely, 
accurate. 

An  estimate  of  the  time  required  for  the  passage  of  the 
whole  mass  of  blood  through  the  heart  is  even  less  definite 
than  the  estimate  of  the  general  rapidity  of  the  circulation. 
To  arrive  at  any  satisfactory  result,  it  is  necessary  to  know  the 
entire  quantity  of  blood  in  the  body,  and  the  exact  quantity 
which  passes  through  the  heart  at  each  pulsation.  If  we 
divide  the  whole  mass  of  blood  by  the  quantity  discharged 
from  the  heart  with  each  systole  of  the  ventricles,  we  ascer- 
tain the  number  of  pulsations  required  for  the  passage  of  the 
whole  mass  of  blood  through  the  heart ;  and,  knowing  the 
number  of  beats  per  minute,  can  ascertain  the  length  of  time 
thus  occupied. 

The  objection  to  this  kind  of  estimate  is  the  inaccuracy 
of  the  data  respecting  the  quantity  of  blood  in  the  system, 
and  the  quantity  which  passes  through  the  heart  with  each 
pulsation.  Nevertheless,  an  estimate  can  be  made,  which, 
if  it  be  not  entirely  accurate,  cannot  be  very  far  from  the 
truth. 

The  entire  quantity  of  blood,  according  to  estimates 
which  seem  to  be  based  on  the  most  reliable  data,  is  about 
one-eighth  the  weight  of  the  body,  or  eighteen  pounds  in  a 
man  weighing  one  hundred  and  forty-four.  The  quantity 
discharged  at  each  ventricular  systole  is  estimated  by  Yalen- 
tin  at  five  ounces,  and  by  Yolkmann  at  six  ounces.1  In 

to  be  28*8  seconds.  In  experimenting  on  the  crural  vein,  this  observer  found 
that  the  circulation  in  the  lower  extremities,  probably  from  the  greater  length  of 
the  vessels,  occupied  from  one  to  three  seconds  more  than  in  the  head. 

1  TODD  and  BOWMAN,  Physiological  Anatomy,  American  edition,  1857,  p.  704. 


348  CIRCULATION. 

treating  of  the  capacity  of  the  different  cavities  of  the  heart, 
it  has  been  noted  that  the  left  ventricle,  when  fully  distend- 
ed, contains  from  five  to  seven  ounces.  Assuming  that  at 
each  systole  the  left  ventricle  discharges  all  its  blood,  except 
perhaps  a  few  drops,  and  that  tins  quantity  in  an  ordinary- 
sized  man  is  five  ounces  (for  in  the  estimates  of  Robin  and 
Hiffelsheim,  the  cavities  were  fully  distended,  and  contained 
more  than  under  the  ordinary  conditions  of  the  circulation),  it 
would  require  fifty-eight  pulsations  for  the  passage  through 
the  heart  of  the  entire  mass  of  blood.  Assuming  the  pulsa- 
tions to  be  seventy-two  per  minute,  this  would  occupy  about 
forty-eight  seconds. 

We  have  given  elsewhere  the  opinions  of  various  physiol- 
ogists on  the  quantity  of  blood  in  the  body,  and  the  capacity 
of  the  cardiac  cavities,  and  shall  not  discuss  the  discordant 
views  on  the  "  duration  of  the  circulation,"  as  each  is  based 
on  different  opinions  regarding  the  two  essential  questions  in 
the  problem.  As  the  quantity  of  blood  in  the  body  is  sub- 
ject to  certain  physiological  variations,  there  should  be  cor- 
responding variations  in  the  duration  of  the  circulation, 
which  it  is  unnecessary  to  take  up  fully  in  this  connection. 

The  almost  instantaneous  action  of  certain  poisons,  which 
must  act  through  the  blood,  confirms  our  ideas  with  regard 
to  the  rapidity  of  the  circulation.  The  intervals  between  the 
introduction  of  some  agents  (strychnine  for  example)  into  the 
circulation,  and  the  characteristic  effects  on  the  system,  have 
been  carefully  noted  by  Blake,1  whose  observations  coincide 
pretty  closely  in  their  results  with  the  experiments  of 
Hering. 

The  relation  of  the  rapidity  of  the  circulation  to  the  fre- 
quency of  the  heart's  action  is  a  question  of  considerable  in- 
terest, which  was  not  neglected  in  the  experiments  of  He- 
ring. It  is  evident  that  if  the  charge  of  blood  sent  into  the 
arteries  be  the  same,  or  nearly  the  same,  under  all  circuin- 

1  Edinburgh  Med.  and  Surgical  Journal,  1840,  vol.  liii.,  p.  35,  and  1841,  voL 
Ivi.,  p.  412. 


GENERAL   EAPIDITr.  349 

stances,  any  increase  in  the  number  of  pulsations  of  the  heart 
would  produce  a  corresponding  acceleration  of  the  general 
current  of  blood.  But  this  is  a  proposition  which  cannot  be 
taken  for  granted;  and  there  are  many  facts  which  favor 
a  contrary  opinion.  It  may  be  enunciated  as  a  general  rule, 
that  when  the  acts  of  the  heart  increase  in  frequency,  they 
diminish  in  force ;  which  renders  it  probable  that  the  ven- 
tricle is  most  completely  distended  and  emptied  when  its  ac- 
tion is  moderately  slow.  When,  however,  the  pulse  is  very 
much  accelerated,  the  increased  number  of  pulsations  of  the 
heart  might  be  sufficient  to  overbalance  the  diminished  force 
of  each  act,  and  increase  the  rapidity  of  the  circulation. 

Hering  has  settled  these  questions  experimentally.  His 
observations  were  made  on  horses  by  increasing  the  frequen- 
cy of  the  pulse,  on  the  one  hand,  physiologically,  by  exercise, 
and  on  the  other  hand,  pathologically,  by  inducing  inflamma- 
tory action.  He  found,  in  the  first  instance,  that  in  a  horse,  with 
the  heart  beating  at  the  rate  of  36  per  minute,  with  8  respi- 
ratory acts,  ferro-cyanide  of  potassium  injected  into  the  jugu- 
lar appeared  in  the  vessel  on  the  opposite  side  after  an  inter- 
val of  from  20  to  25  seconds.  By  exercise,  the  number  of 
pulsations  was  raised  to  100  per  minute,  and  the  rapidity 
of  the  circulation  was  from  15  to  20  seconds.  The  observa- 
tions were  made  with  an  interval  of  24  hours.  The  same 
results  were  obtained  in  other  experiments.1  Here  there  is 
a  considerable  increase  in  the  rapidity  of  the  circulation  fol- 
. lowing  a  physiological  increase  in  the  number  of  beats  of  the 
heart ;  but  the  value  of  each  beat  is  materially  diminished  ; 
otherwise  the  rapidity  of  the  current  would  be  increased 
about  three  times,  as  the  pulse  became  three  times  as  frequent. 
In  its  tranquil  action,  with  the  pulse  at  36,  the  heart  con- 
tracted thirteen  times  during  one  circuit  of  blood ;  while  it 
required  twenty-nine  pulsations  to  send  the  blood  over  the 
same  course,  after  exercise,  with  the  pulse  at  100 ;  showing  a 

MILNE-EDWARDS,  Lemons  sur  la  Physiologic,  tome  ir.,  p.  371,  note. 


350  CIRCULATION. 

diminution  in  the  value  of  the  ventricular  systole  of  more 
than  one-half. 

In  animals  suffering  under  inflammatory  fever,  either 
spontaneous  or  produced  by  irritants,  the  same  observer 
found  a  diminution  in  the  rapidity  of  the  circulation,  accom- 
panying acceleration  of  the  pulse.  In  one  observation,  in- 
flammation was  produced  in  the  horse  by  the  injection  of 
ammonia  into  the  pericardium.  At  the  commencement  of  the 
experiment,  the  pulse  was  from  Y2  to  84:  per  minute,  and  the 
duration  of  the  circulation  about  25  seconds.  The  next  day, 
with  the  pulse  at  90,  the  circulation  was  accomplished  in 
from  35  to  40  seconds ;  and  the  day  following,  with  the  pulse 
at  100,  the  rapidity  of  the  circulation  was  diminished  to  from 
40  to  45  seconds. 

If  we  are  justified  in  applying  these  observations  to  the 
human  subject  (and  there  is  no  reason  why  this  should  not 
be  done),  it  is  shown  that  when  the  pulse  is  accelerated  in 
disease,  the  value  of  the  contractions  of  the  heart,  as  rep- 
resented by  the  quantity  of  blood  discharged,  bears  an 
inverse  ratio  to  their  number;  and  is  so  much  diminished 
as  absolutely  to  produce  a  current  of  less  rapidity  than 
normal. 

"With  regard  to  the  relations  between  the  rapidity  of  the 
heart's  action  and  the  general  rapidity  of  the  circulation,  the 
following  conclusions  may  be  given  as  the  result  of  experi- 
mental inquiry : 

1.  In  physiological  increase  in  the  number  of  beats  of  the 
hear^  as  the  result  of  exercise,  for  example,  the  general  circu- 
lation is  somewhat  increased  in  rapidity,  though  not  in  pro- 
portion to  the  increase  in  the  pulse. 

2.  In  pathological  increase  of  the  hearts  action,  as  in 
febrile  movement,  the  rapidity  of  the  general  circulation  is 
generally  diminished,  it  may  be,  to  a  very  great  extent. 

3.  Whenever  the  number  of  beats  of  the  heart  is  consider- 
ably increased  from  any  cause,  the  quantity  of  Hood  dis- 
charged at  each  ventricular  systole  is  very  much  diminished, 


CIRCULATION  AFTER  DEATH.  351 

either  from  lack  of  complete  distention,  or  from  imperfect 
emptying  of  the  cavities.1 

Phenomena  in  the  Circulatory  System  after  Death.— -We 
do  not  believe  that  any  one  has  proven  the  existence  of  a 
force  in  the  capillaries  or  the  tissues  (capillary  power)  which 
materially  assists  the  circulation  during  life,  or  produces  any 
movement  immediately  after  death;  and  shall  not  discuss 
further  the  extraordinary  post-mortem  phenomena  of  circu- 
lation, particularly  those  which  have  been  observed  by  Dr. 
Dowler  in  subjects  dead  of  yellow  fever.1  But  nearly  every 
autopsy  shows  that  after  death  the  blood  does  not  remain 
equally  distributed  in  the  arteries,  capillaries,  and  veins. 
Influenced  by  gravitation,  it  accumulates  in  and  discolors  the 
most  dependent  parts  of  the  body.  The  arteries  are  always 
found  empty,  and  all  the  blood  in  the  body  accumulates  in 
the  venous  system  and  capillaries ;  a  fact  which  was  observed 
by  the  ancients,  and  gave  rise  to  the  belief  that  the  arteries, 
as  their  name  implies,  were  air-bearing  tubes. 

This  phenomenon  has  long  engaged  the  attention  of  phys- 
iologists, who  have  attempted  to  explain  it  by  various 
theories.  Without  discussing  the  views  on  this  subject  an- 
terior to  our  knowledge  of  the  great  contractile  power  of  the 
arteries  as  compared  with  other  vessels,  we  may  cite  the  ex- 
periment of  Magendie,  already  referred  to,2  as  offering  a 
satisfactory  explanation.  If  the  artery  and  vein  of  a  limb  be 
exposed  in  a  living  animal,  and  all  the  other  vessels  be  tied, 
compression  of  the  artery  does  not  immediately  arrest  the 
current  in  the  vein,  but  the  blood  will  continue  to  flow  until 
the  artery  is  entirely  emptied.  The  artery,  when  relieved 

1  These  great  variations  in  the  value  of  the  ventricular  systole,  amounting 
even,  in  the  experiment  on  the  healthy  animal,  to  a  diminution  of  one-half,  as  the 
result  of  exercise,  show  the  uncertainty  of  the  basis  of  those  estimates  with  regard 
to  the  time  required  for  the  entire  mass  of  blood  to  pass  through  the  heart,  which 
are  calculated  from  the  entire  quantity  of  blood,  the  quantity  discharged  from  the 
heart  at  each  pulsation,  and  the  number  of  pulsations  per  minute. 

2  See  page  295. 


352  CIRCULATION. 

from  the  distending  force  of  the  heart,  reacts  on  its  contents 
by  virtue  of  its  contractile  coat,  and  completely  empties  itself 
of  blood.  An  action  similar  to  this  takes  place  after  death 
throughout  the  entire  arterial  system.  The  vessels  react  on 
their  contents,  and  gradually  ^force  all  the  blood  into  and 
through  the  capillaries,  which  are  very  short,  to  the  veins, 
which  are  capacious,  distensible,  and  but  slightly  contractile. 
This  begins  immediately  after  death,  while  the  irritability  of 
the  muscular  coat  of  the  arteries  remains,  and  is  seconded  by 
the  subsequent  cadaveric  rigidity,  which  affects  all  the  in- 
voluntary, as  well  as  the  voluntary  muscular  fibres.  Once  in 
the  venous  system,  the  blood  cannot  return  on  account  of  the 
valves.  Thus  after  death  the  blood  is  found  in  the  veins  and 
capillaries  of  dependent  parts  of  the  body. 


CHAPTEE  X. 

RESPIRATION. 

General  considerations — Physiological  anatomy  of  the  respiratory  organs — Respi- 
ratory movements  of  the  larynx — Epiglottis — Trachea  and  bronchial  tubes — 
Parenchyma  of  the  lungs — Carbonaceous  matter  in  the  lungs — Movements  of 
respiration — Inspiration — Muscles  of  inspiration — Action  of  the  diaphragm — 
Action  of  the  scaleni — Intercostal  muscles — Levatores  costarum — Auxiliary 
muscles  of  inspiration. 

THE  characters  of  the  blood  are  by  no*  means  identical  in 
the  great  divisions  of  the  vascular  system ;  but  thus  far,  phys- 
iologists have  been  able  to  investigate  only  the  differences 
which  exist  between  arterial  and  venous  blood ;  for  the  capil- 
laries are  so  short,  communicating  directly  with  the  arteries 
on  the  one  side  and  the  veins  on  the  other,  that  it  has  been 
impossible  to  obtain  a  specimen  of  blood  which  can  be  said 
to  belong  to  this  system.  In  the  capillaries,  however,  the 
nutritive  fluid,  which  is  identical  in  all  parts  of  the  arterial 
system,  undergoes  a  remarkable  change,  rendering  it  unfit 
for  nutrition.  It  is  then  known  as  venous  blood;  and, 
as  we  have  seen,  the  only  office  of  the  veins  is  to  carry  it 
back  to  the  right  side  of  the  heart,  to  be  sent  to  the  lungs, 
where  it  loses  the  vitiating  materials  it  has  collected  in  the 
tissues,  takes  in  a  fresh  supply  of  the  vivifying  oxygen,  and 
goes  to  the  left  or  systemic  heart,  again  prepared  for  nutri- 
tion. As  the  processes  of  nutrition  vary  in  different  parts  of 
the  organism,  necessarily,  there  are  corresponding  variations 
23 


354 


RESPIRATION. 


in  the  composition  of  the  blood  throughout  the  venous 
system. 

The  important  principles  which  are  given  off  by  the 
lungs  are  exhaled  from  the  blood  ;  and  the  gas  which  disap- 
pears from  the  air  is  absorbed  by  the  blood,  mainly  by  its 
corpuscular  elements. 

A  proper  supply  of  oxygen  is  indispensable  to  nutrition, 
and  even  to  the  comparatively  mechanical  process  of  circula- 
tion ;  but  it  is  no  less  necessary  to  the  vital  processes  that 
carbonic  acid,  which  the  blood  acquires  in  the  tissues,  should 
be  given  off. 

Respiration  may  1)6  defined  to  1)6  the  process  by  which 
the  system  receives  oxygen,  and  is  relieved  of  carbonic  acid. 

As  it  is  almost  exclusively  through  the  blood  that  the 
tissues  and  organs  are  supplied  with  oxygen,  and  as  the 
blood  receives  and  exhales  most  of  the  carbonic  acid,  the  re- 
spiratory process  may  be  said  to  consist  chiefly  in  the  change 
of  venous  into  arterial  blood.  But  experiments  have  demon- 
strated that  the  tissues  themselves,  detached  from  the  body 
and  placed  in  an  atmosphere  of  oxygen,  will  absorb  this  gas 
and  exhale  carbonic  acid.1  Under  these  circumstances,  they 
certainly  respire,  and  it  is  evident,  therefore,  that  in  this 
process  the  intervention  of  the  blood  is  not  an  absolute 
necessity. 

The  tide  of  air  in  the  lungs  does  not  constitute  respiration, 
as  we  now  understand  it.  These  organs  only  serve  to  facili- 
tate the  introduction  of  air  into  the  blood,  and  the  exhalation 
of  carbonic  acid.  If  the  system  be  drained  of  blood,  or  if  the 
blood  be  rendered  incapable  of  interchanging  its  gases  with 
the  air,  respiration  ceases,  and  all  the  phenomena  of  asphyxia 
are  presented,  though  air  be  introduced  into  the  lungs  with 

1  G.  Liebig  demonstrated  that  the  muscles  of  the  frog,  separated  from  the 
body  and  carefully  freed  from  blood,  will  continue  to  absorb  oxygen  and  exhale 
carbonic  acid  as  long  as  they  retain  their  irritability.  (LEHMANN,  Physiological 
Chemistry,  Philadelphia,  1855,  vol.  ii.,  pp.  247,  474.) 


GENERAL   CONSIDERATIONS.  355 

the  utmost  regularity.  It  must  be  remembered  that  the  es- 
sential processes  of  respiration  take  place  in  all  the  tissues 
and  organs  of  the  system,  and  not  in  the  lungs.  Respiration 
is  a  process  similar  to  what  are  known  as  the  processes  of 
nutrition  ;  and  although  it  is  much  more  active  and  uniform, 
as  far  as  its  products  are  concerned,  than  the  ordinary  nutri- 
tive acts,  it  is  inseparably  connected  with,  and  strictly  a  part 
of  the  general  process.  As  in  the  nutrition  of  the  substance 
of  tissues,  certain  principles  of  the  blood,  fibrin  and  albu- 
men, for  example,  united  with  inorganic  principles,  are  used 
up,  transformed  into  the  tissue  itself,  finally  changed  into 
excrementious  products,  such  as  urea  or  cholesterine,  and  dis- 
charged from  the  body,  so  the  oxygen  of  the  blood  is  appro- 
priated, and  carbonic  acid,  which  is  an  excrementitious  prod- 
uct, produced  whenever  tissues  are  worn  out  and  regener- 
ated. There  is  a  necessary  and  inseparable  connection  be- 
tween all  these  processes ;  and  they  must  be  considered,  not 
as  distinct  functions,  but  as  different  parts  of  the  one  great 
function  of  nutrition.  As  we  are  as  yet  unable  to  follow  out 
all  the  changes  which  take  place  between  the  appropriation 
of  nutritive  materials  from  the  blood,  and  the  production  of 
effete  or  excrementitious  substances,  it  is  impossible  to  say 
precisely  how  the  oxygen  is  used  by  the  tissues,  and  how  the 
carbonic  acid  is  produced.  We  only  know  that  more  or  less 
oxygen  is  necessary  to  the  nutrition  of  all  tissues,  in  all  ani- 
mals, high  or  low  in  the  scale,  and  that  they  produce  a  cer- 
tain quantity  of  carbonic  acid.  The  fact  that  oxygen  is  con- 
sumed with  much  greater  rapidity  than  any  other  nutritive 
principle,  and  that  the  production  of  carbonic  acid  is  corre- 
spondingly active,  as  compared  with  other  effete  products, 
points  pretty  conclusively  to  a  connection  between  the  ab- 
sorption of  the  one  principle  and  the  production  of  the  other. 
In  asphyxia,  indeed,  it  is  difficult  to  say  which  destroys 
life,  the  absence  of  oxygen  or  the  accumulation  of  carbonic 
acid. 

In  some  of  the  lowest  of  the  inferior  animals,  there  is 


356  RESPIRATION. 

no  special  respiratory  organ,  the  interchange  of  gases  being 
effected  through  the  general  surface.  Higher  in  the  animal 
scale,  special  organs  are  found,  which  are  called  gills,  when 
the  animals  live  under  water  and  respire  the  air  which  is  in 
solution  in  the  water,  and  lung^  when  the  air  is  introduced 
in  its  gaseous  form.1  Animals  possessed  of  lungs  have  a  tol- 
erably perfect  circulatory  apparatus,  so  that  the  blood  is 
made  to  pass  continually  through  the  respiratory  organs.  In 
the  human  subject  and  warm-blooded  animals  generally,  the 
lungs  are  very  complex,  and  present  an  immense  surface 
by  which  the  blood  is  exposed  to  the  air,  only  separated  from 
it  by  a  delicate  permeable  membrane.  These  animals  are 
likewise  provided  with  a  special  heart,  which  has  the  duty  of 
carrying  on  the  pulmonary  circulation.  Though  respiration 
is  carried  on  to  some  extent  by  the  general  surface,  the  lungs 
are  the  important  and  essential  organs  in  which  the  inter 
change  of  gases  takes  place. 

The  essential  conditions  for  respiration  in  animals  which 
have  a  circulating  nutritive  fluid  are  :  air  and  Nood,  sepa- 
rated by  a  membrane  which  will  allow  the  passage  of  gases. 
The  effete  products  of  respiration  in  the  blood  pass  out  and 
vitiate  the  air.  The  air  is  deprived  of  a  certain  portion  of  its 
oxygen,  which  passes  into  the  blood,  to  be  conveyed  to 
the  tissues.  Thus  the  air  must  be  changed  to  supply  fresh 
oxygen  and  get  rid  of  the  carbonic  acid.  The  rapidity  of 
this  change  is  in  proportion  to  the  nutritive  activity  of  the 
animal  and  the  rapidity  of  the  circulation  of  the  blood.2 

1  Insects  have  no  lungs  ;  but  the  air  is  disseminated  throughout  the  organism 
by  a  system  of  air-bearing  tubes  (true  arteries),  or  tracheas,  and  is  probably  ap- 
propriated directly  by  the  tissues,  without  the  intervention  of  the  blood. 

2  The  manner  in  which  this  change  of  air  is  effected  in  the  different  classes  of 
animals  constitutes  one  of  the  most  interesting  subjects  in  comparative  physiology. 
Its  study  has  shown  how,  as  we  pass  from  the  lower  to  the  higher  orders  of  ani- 
mals, and  the  functions  become  more  active,  a  division  of  labor  takes  place. 
Functions  which  in  the  lowest  animals  have  no  special  organs,  one  part,  as  the 
integument  or  alimentary  track,  performing  many  offices,  in  the  higher  classes 
are  assigned  to  special  organs,  which  are  brought  to  a  high  condition  of  develop- 


ANATOMY   OF   THE  RESPIRATORY   ORGANS.  357 

In  treating  in  detail  of  the  function  of  respiration,  it  will 
be  convenient  to  make  the  following  division  of  the  subject: 

1.  The  mechanical  phenomena  of  respiration ;  or  the  pro- 
cesses by  which  the  fresh  air  is  introduced  into  the  lungs 
(inspiration),  and  the  vitiated  air  is  expelled  (expiration). 

2.  The  changes  which  the  air  undergoes  in  respiration. 

3.  The  changes  which  the  blood  undergoes  in  respiration. 

4.  The  relations  of  the  consumption  of  oxygen  and  the 
production  of  carbonic  acid  to  the  general  process  of  nutri- 
tion. 

5.  The  respiratory  sense ;  a  want,  on  the  part  of  the  sys- 
tem, which  induces  the  respiratory  acts  (besoin  de  respirer}. 

6.  Cutaneous  respiration. 

7.  Asphyxia. 

The  study  of  these  questions  will  be  facilitated  by  a  brief 
consideration  of  some  points  in  the  anatomy  of  the  respira- 
tory organs. 

Physiological  Anatomy  of  the  Respiratory  Organs. 

Passing  backward  from  the  mouth  to  the  pharynx,  two 
openings  present  themselves:  one,  posteriorly,  which  leads  to 
the  oesophagus,  and  one,  anteriorly,  the  opening  of  the  larynx, 
which  is  the  commencement  of  the  passages  devoted  exclu- 
sively to  respiration.  The  construction  of  the  oesophagus  and 
the  air-tubes  is  entirely  different.  The  oesophagus  is  flaccid, 
and  destined  to  receive  and  convey  to  the  stomach  the  ar- 
ticles of  food  which  are  introduced  by  the  constrictions  of  the 
muscles  above.  The  trachea  and  its  ramifications  are  exclu- 
sively for  the  passage  of  air,  which  is  taken  in  by  a  suction 
force  produced  by  the  enlargement  of  the  thorax.  The  act 
of  inhalation  requires  that  the  tubes  should  be  kept  open  by 

ment.  The  perfection  of  organization  in  the  higher  animals  seems  to  consist  in 
the  multiplication  of  organs,  for  the  more  efficient  performance  of  the  various 
functions. 


358  RESPIRATION. 

walls  sufficiently  rigid  to  resist  the  external  pressure  of  the 
air. 

Commencing  with  the  larynx,  it  is  seen  that  the  cartilages 
of  which  it  is  composed  are  sufficiently  rigid  and  unyield- 
ing to  resist  the  pressure  produced  by  any  inspiratory 
effort.  Across  its  superior  opening  are  the  yocal  cords, 
which  are  four  in  number,  and  have  a  direction  from  before 
backwards.  The  two  superior  are  called  the  false  vocal 
cords,  because  they  are  not  concerned  in  the  production  of 
the  voice.  The  two  inferior  are  the  true  vocal  cords.  They  are 
ligamentous  bands  covered  by  folds  of  mucous  membrane, 
which  is  quite  thick  on  the  superior  cords,  and  very  thin  and 
delicate  on  the  inferior.  Anteriorly,  they  are  attached  to  a 
fixed  point  between  the  thyroid  cartilages,  and  posteriorly, 
to  the  movable  arytenoid  cartilages.  Air  is  admitted  to  the 
trachea  through  an  opening  between  the  cords,  which  is 
called  the  rima  glottidis.  Little  muscles,  arising  from  the 
thyroid  and  cricoid,  and  attached  to  the  arytenoid  cartilages, 
are  capable  of  separating  and  approximating  the  points 
to  which  the  vocal  cords  are  attached  posteriorly,  so  as  to 
open  and  close  the  rima  glottidis. 

If  the  glottis  be  exposed  in  a  living  animal,  certain  regu- 
lar movements  are  presented  which  are  synchronous  with  the 
acts  of  respiration.  The  larynx  is  widely  opened  at  each  in- 
spiration by  the  action  of  the  muscles  referred  to  above,  so 
that  the  air  has  a  free  entrance  to  the  trachea.  At  the  ter- 
mination of  the  inspiratory  act,  these  muscles  are  relaxed, 
the  vocal  cords  fall  together  by  their  own  elasticity,  and  in 
expiration,  the  chink  of  the  glottis  returns  to  the  condition 
of  a  narrow  slit.  These  respiratory  movements  of  the  glottis 
are  constant,  and  essential  to  the  introduction  of  air  in 
proper  quantity  to  the  lungs.  The  expulsion  of  air  from  the 
lungs  is  rather  a  passive  process,  and  tends  in  itself  to  sepa- 
rate the  vocal  cords ;  but  inspiration,  which  is  active  and 
more  violent,  were  it  not  for  the  movements  of  the  glottis, 
would  have  a  tendency  to  draw  the  vocal  cords  together. 


EESPDRATOBY  MOVEMENTS   OF  THE   GLOTTIS.  359 

The  muscles  which,  are  engaged  in  producing  these  move- 
ments are  animated  by  the  inferior  laryngeal  branches  of 
the  pneumogastric  nerves.  If  these  nerves  be  divided,  the 
movements  of  the  glottis  are  arrested,  and  respiration  is 
very  seriously  interfered  with.  This  is  particularly  marked 
in  young  animals,  in  which  the  walls  of  the  larynx  are  com- 
paratively yielding,  when  the  operation  is  frequently  followed 
by  immediate  death  from  suffocation.  The  movements  of 
the  glottis  enable  us  to  understand  how  foreign  bodies  of 
considerable  size  are  sometimes  accidentally  introduced  into 
the  air-passages. 

The  respiratory  movements  of  the  larynx  are  entirely  dis- 
tinct from  those  engaged  in  the  production  of  the  voice,  and 
are  simply  for  the  purpose  of  facilitating  the  entrance  of  air 
in  inspiration. 

Attached  to  the  anterior  portion  of  the  larynx  is  the  epi- 
glottis ;  a  little  leaf-shaped  lamella  of  fibro-cartilage,  which, 
during  ordinary  respiration,  projects  upward,  and  lies  against 
the  posterior  portion  of  the  tongue.  During  the  act  of  de- 
glutition, respiration  is  momentarily  interrupted,  and  the  air- 
passages  are  protected  by  the  tongue,  which  presses  backward 
carrying  the  epiglottis  before  it,  completely  closing  the  open- 
ing of  the  larynx.  Physiologists  have  questioned  whether 
the  epiglottis  be  necessary  for  the  complete  protection  of  the 
air-passages ;  and,  repeating  the  experiments  of  Magendie,  it 
has  been  frequently  removed  from  the  lower  animals  without 
apparently  interfering  with  the  proper  deglutition  of  solids 
or  liquids.  We  have  been  satisfied  from  actual  experiment 
that  a  dog  will  swallow  liquids  and  solids  immediately  after 
the  ablation  of  the  epiglottis,  without  allowing  any  to  pass 
into  the  trachea ;  but  it  becomes  a  question  whether  this  ex- 
periment can  be  absolutely  applied  to  the  human  subject. 
In  a  case  of  entire  loss  of  the  epiglottis,  which  was  observed 
in  the  Bellevne  Hospital,  the  patient  experienced  slight 
difficulty  in  swallowing,  from  the  passage  of  little  parti- 
cles into  the  larynx,  which  produced  cough.  Tljis-  case 


360  RESPIRATION. 

seemed  to  show  that  the  presence  of  the  epiglottis,  in  the 
human  subject  at  least,  is  necessary  to  the  complete  protec- 
tion of  the  air-passages  in  deglutition.1 

Passing  down  the  neck  from  the  larynx  toward  the  lungs, 
is  a  tube,  from  four  to  four  an$  a  half  inches  in  length,  and 
about  three-quarters  of  an  inch  in  diameter,  which  is  called 
the  trachea.  It  is  provided  with  cartilaginous  rings,  from 
sixteen  to  twenty  in  number,  which  partially  surround  the 
tube,  leaving  about  one-third  of  its  posterior  portion  occupied 
by  fibrous  tissue,  mixed  with  a  certain  number  of  unstriped 
muscular  fibres.  Passing  into  the  chest,  the  trachea  divides 
into  the  two  primitive  bronchi;  the  right  being  shorter, 
larger,  and  more  horizontal  than  the  left.  These  tubes,  pro- 
vided, like  the  trachea,  with  imperfect  cartilaginous  rings, 
enter  the  lungs,  divide  and  subdivide,  until  the  minute  rami- 
fications of  the  bronchial  tree  open  directly  into  the  air-cells. 
After  penetrating  the  lungs,  the  cartilages  become  irregular, 
and  are  in  the  form  of  angular  plates,  which  are  so  disposed 
as  to  completely  encircle  the  tubes.  In  tubes  of  very  small 
size,  these  plates  are  less  numerous  than  in  the  larger  bronchi, 
until  in  tubes  of  a  less  diameter  than  -^  of  an  inch,  they  are 
lost  altogether. 

The  walls  of  the  trachea  and  bronchial  tubes  are  com- 
posed of  two  distinct  membranes :  an  external  membrane, 
between  the  layers  of  which  the  cartilages  are  situated,  and  a 
lining  mucous  membrane.  The  external  membrane  is  com- 
posed of  inelastic  and  elastic  fibrous  tissue.  Posteriorly,  in 
the  space  not  covered  by  cartilaginous  rings,  these  fibres  are 
mixed  with  a  certain  number  of  unstriped  or  involuntary 
muscular  fibres,  which  exist  in  two  layers :  a  thick  internal 
layer,  in  which  the  fibres  are  transverse,  and  a  thinner  longi- 
tudinal layer,  which  is  external.  This  collection  of  muscular 
fibres  is  sometimes  called  the  trachealis  muscle.  Throughout 

1  This  remarkable  case,  in  which  the  epiglottis  had  sloughed  entirely  away 
leaving  the  parts  completely  cicatrized,  as  demonstrated  by  a  laryngOscopic  exam- 
ination, will  be  given  in  eztenso  in  connection  with  the  subject  of  deglutition. 


PARENCHYMA  OF  THE  LUNGS.  361 

the  entire  system  of  bronchial  tubes,  there  are  circular  fasciculi 
of  muscular  fibres  lying  just  beneath  the  mucous  membrane, 
with  a  number  of  longitudinal  elastic  fibres.  The  character 
of  the  bronchi  abruptly  changes  in  tubes  less  than  -^  of  an 
inch  in  diameter.  They  lose  the  cartilaginous  rings,  and  the 
external  and  the  mucous  membranes  become  so  closely  united 
that  they  can  no  longer  be  separated  by  dissection.  The 
circular  muscular  fibres  continue  down  to  the  air-cells.  The 
mucous  membrane  is  smooth,  covered  by  ciliated  epithelium, 
the  movements  of  the  ciliae  being  always  from  within  out- 
ward, and  it  is  provided  with  numerous  mucous  glands.  These 
glands  are  of  the  racemose  variety,  and  in  the  larynx  are  of 
considerable  size.  In  the  trachea  and  bronchi,  racemose 
glands  exist  in  the  membrane  on  the  posterior  surface  of 
the  tubes ;  but  anteriorly  are  small  follicles,  terminating  in 
a  single,  and  sometimes  a  double,  blind  extremity.  These 
follicles  are  lost  in  tubes  less  than  -g1-^  of  an  inch  in  diameter. 
It  is  the  anatomy  of  the  parenchyma  of  the  lungs  which 
possesses  the  most  physiological  interest,  for  here  the  essential 
processes  of  respiration  take  place.  When  moderately  in- 
flated, the  lungs  have  the  appearance  of  irregular  cones,  with 
rounded  apices,  and  concave  bases  resting  upon  the  diaphragm. 
They  fill  all  of  the  cavity  of  the  chest  which  is  not  occupied 
by  the  heart  and  great  vessels,  and  are  completely  separated 
from  each  other  by  the  mediastinum.  In  the  human  subject, 
the  lungs  are  not  attached  to  the  thoracic  walls,  but  are 
closely  applied  to  them,  each  covered  by  a  reflection  of  the 
serous  membrane  which  lines  the  cavity  on  the  corresponding 
side.  They  thus  necessarily  follow  the  movements  of  ex- 
pansion and  contraction  of  the  thorax.  Deep  fissures  divide 
the  right  lung  into  three  lobes,  and  the  left  lung  into  two. 
The  surface  of  the  lungs  is  divided  into  irregularly  polygonal 
spaces,  from  J  of  an  inch  to  an  inch  in  diameter,  which  mark 
what  are  sometimes  called  the  pulmonary  lobules,  though 
this  term  is  incorrect,  as  each  of  these  divisions  includes 
quite  a  number  of  the  true  lobules. 


362 


"RESPIRATION. 


Following  out  the  bronchial  tubes  from  the  diameter  of 
fa  of  an  inch,  the  smallest,  which  are  from  yfo  to  fa  of  an 
inch  in  diameter,  open  into  a  collection  of  oblong  vesicles, 
Kg.  10.  which  are  the   air- 

cells.  Each  collec- 
tion of  vesicles  con- 
stitutes one  of  the 
true  pulmonary  lo- 
bules, and  is  from 
fa  to  fa  of  an  inch 
in  diameter.  After 
entering  the  lobule, 
the  tube  forms  a  sort 
of  tortuous  central 
canal,  sending  off 
branches  which  ter- 
minate in  groups  of 
from  eight  to  fifteen 
pulmonary  cells. 
The  cells  are  a  little 
deeper  than  they  are 
wide,  and  have  a 
rounded  blind  ex- 
tremity. Some  are 
smooth,  but  many 

(After  Eobin.)  are  marked  by  little 

circular  constrictions,  or  rugse.  In  the  healthy  lung  of  the 
adult,  after  death,  they  measure  from  -^  to  T|o-  or  fa  of  an 
inch  in  diameter,  but  are  capable  of  very  great  distention. 
The  smallest  cells  are  in  the  deep  portions  of  the  lungs,  and 
the  largest  are  situated  near  the  surface.  By  sections  of  lung 
inflated  and  dried,  Magendie  demonstrated,  a  number  of 
years  ago,  that  there  is  a  considerable  variation  in  the  size 
of  the  cells  at  different  periods  of  life ;  that  the  smallest 
cells  are  found  in  young  children,  and  that  they  progres- 


Mould  of  a  terminal  bronchus  and  a  group  of  air-cells 
moderately  distended  by  injection,  from  the  human  subject. 


PARENCHYMA  OF  THE  LUNGS.  363 

sively  increase  in  size  with  age.1  The  air-cells  are  sur- 
rounded by  a  great  number  of  elastic  fibres,  which  do  not 
form  distinct  bundles  for  each  cell,  but  anastomose  freely 
with  each  other,  so  that  the  same  fibres  belong  to  two  or 
more.  This  structure  is  peculiar  to  the  parenchyma  of  the 
lungs,  and  gives  these  organs  their  great  distensibility  and 
elasticity,  properties  which  play  an  important  part  in  ex- 
pelling the  air  from  the  chest,  as  a  consequence  simply  of 
cessation  of  the  action  of  the  inspiratory  muscles.  Inter- 
woven with  these  elastic  fibres  is  the  richest  plexus  of 
capillary  blood-vessels  found  in  the  economy.  The  vessels 
are  larger  than  the  capillaries  in  other  situations,  and  the 
plexus  is  so  close  that  the  spaces  between  them  are  narrower 
than  the  vessels  themselves.  When  distended,  the  blood-ves- 
sels form  the  greater  part  of  the  walls  of  the  cells. 

There  is  some  difference  of  opinion  among  anatomists  with 
regard  to  the  lining  of  the  air-cells.  Some  are  of  the  opinion, 
with  Rainey  and  Mandl,  that  the  mucous  membrane,  and 
even  the  epithelium,  cease  in  the  small  bronchial  tubes,  and 
the  blood-vessels  in  the  cells  are  uncovered.  The  presence  of 
pavement  epithelium  has  been  demonstrated,  however,  in  the 
cells,  but  the  scales  are  detached  soon  after  death,  and  cannot 
always  be  observed.  All  who  contend  for  the  existence  of  a 
mucous  membrane  admit  that  it  is  of  excessive  tenuity. 
Robin,  Kolliker,  and  others  have  demonstrated  in  the  air- 
cells  very  thin  scales  of  pavement  epithelium,  from  -g-^L-o-  *° 
•jroVo  °f  an  incn  i*1  diameter,  which  are  applied  directly  to  the 
walls  of  the  blood-vessels.2  The  epithelium  here  does  not 
seem  to  be  regularly  desquamated,  as  in  other  situations. 
Examination  of  injected  specimens  shows  that  the  blood-ves- 
sels are  so  situated  between  the  cells,  that  the  blood  in  the 
greater  part  of  their  circumference  is  exposed  to  the  action 
of  the  air. 

1  MAGENDIE,  Memoire  sur  la  /Structure  du  Poumon  de  THomme. — Journal  de 
Physiologic,  1821,  tome  i.,  p.  V8. 

a  KOLLIKER,  Manual  of  Human  Microscopic  Anatomy,  London,  1860,  p.  387 ; 
and  POUCHET,  Histologie  Humaine,  Paris,  1864,  p.  286. 


364:  RESPIRATION. 

The  entire  mass  of  venous  blood  is  distributed  in  the  lungs 
by  the  pulmonary  artery  for  the  purposes  of  aeration.  Arte- 
rial blood  is  conveyed  to  these  organs  by  the  bronchial  arte- 
ries, which  ramify  and  subdivide  on  the  bronchial  tubes,  and 
follow  their  course  into  the  lyings,  for  the  nourishment  of 
these  parts.  It  is  possible  that  the  tissue  of  the  lungs  may 
receive  some  nourishment  from  the  blood  conveyed  there  by 
the  pulmonary  artery  ;  but  as  this  vessel  does  not  send  any 
branches  to  the  bronchial  tubes,  it  is  undoubtedly  the  bron- 
chial arteries  which  supply  the  material  for  their  nutrition 
and  the  secretion  of  the  mucous  glands.  This  is  one  of  the 
anatomical  reasons  why  inflammatory  conditions  of  the  bron- 
chial tubes  do  not  extend  to  the  parenchyma  of  the  lungs,  and 
vice  versa. 

The  foregoing  anatomical  sketch  shows  the  admirable 
adaptation  of  the  trachea  and  bronchial  tubes  to  the  pas- 
sage of  the  air  by  inspiration  to  the  deep  portions  of  the 
lungs,  and  the  favorable  conditions  which  it  there  meets  with 
for  an  interchange  of  the  elements  of  the  air  and  blood.  It 
is  also  evident,  from  the  enormous  number  of  air-cells,  that 
the  respiratory  surface  must  be  immense.1 

Carbonaceous  Matter  in  the  Lungs. — The  lungs  of  most 
of  the  inferior  animals  and  the  human  subject,  in  early  life, 
have  a  uniform  rose  tint ;  but  in  the  adult,  and  particularly 
in  old  age,  they  contain  a  greater  or  less  quantity  of  black 
matter,  which  may  exist  in  little  masses,  deposited  here  and 
there  in  the  pulmonary  structure,  or  forming  lines  on  the 

1  Hales  estimated  the  combined  surface  of  the  air-cells  at  289  square  feet 
(Statical  Essays,  voL  i.,  p.  242)  ;  Keill  at  21,906  square  inches  (Essays  on  Several 
Parts  of  the  Animal  (Economy,}).  122);  and  Lieberkiihn  at  1,500  square  feet 
(DUNGLISON'S  Human  Physiology,  1856,  vol.  i.,  p.  278).  There  are  not  sufficient 
data  on  this  point  for  us  to  form  any  thing  like  a  reliable  estimate.  It  is 
simply  evident  that  the  extent  of  surface  must  be  very  great.  In  passing  from 
the  lower  to  the  higher  orders  of  animals,  it  is  seen  that  Nature  provides  for 
the  necessity  of  an  increase  in  the  activity  of  the  respiratory  process,  by  a 
ished  size  and  a  multiplication  of  the  air-cells. 


CARBONACEOUS   MATTER   IN  THE   LUNGS.  365 

surface  of  the  organs.  The  deposit  is  generally  most  abun- 
dant at  the  summit  of  the  lungs.  This  matter  also  exists  in 
the  lymphatic  glands  connected  with  the  pulmonary  struc- 
ture, which  are  sometimes  called  the  u  bronchial  glands." 
The  nature  of  this  deposit  has  been  the  subject  of  consider- 
able discussion.  Some  have  supposed  that  it  was  connected 
with  melanotic  deposits,  and  consisted  of  ordinary  pigmentary 
matter ;  but  chemical  investigations  have  now  pretty  conclu- 
sively demonstrated  that  it  is  nothing  more  nor  less  than 
carbon.  It  exists  in  great  abundance  in  the  lungs  of  miners, 
who  inhale  great  quantities  of  carbonaceous  particles,  and  of 
those  who  are  much  exposed  to  the  inhalation  of  smoke. 
These  facts,  taken  in  connection  with  its  absence  in  young 
persons  and  the  inferior  animals,  and  its  small  quantity,  even 
in  old  age,  in  those  who  inhabit  villages  and  are  not  exposed 
to  a  smoky  atmosphere,  point  to  its  introduction  from  with- 
out. The  subject  has  been  most  completely  and  ably  inves- 
tigated by  Robin,  wrho  has  come  to  the  conclusion  that  the 
matter  is  really  carbon  ;  that  it  is  introduced  in  fine  particles 
in  the  inspired  air,  and  that,  once  in  the  lungs,  it  penetrates 
the  tissue,  not  by  absorption,  but  by  mechanical  action,  until  it 
finds  its  way  beneath  the  pleura  and  into  the  intercellular 
substance.  From  the  fact  that  carbon  is  insoluble,  its  penetra- 
tion must  be  mechanical ;  and,  when  found  in  the  lymphatic- 
glands,  it  is  carried  there  by  the  absorbent  vessels.  When 
it  has  penetrated  the  substance  of  the  tissues,  it  can  no  more 
be  removed  than  the  tattooing  beneath  the  skin ;  indeed,  the 
deposition  in  the  lungs  may  be  compared  very  aptly  to  the 
process  of  tattooing. 

The  mechanism  of  its  introduction  is  the  following  :  The 
little  sharp,  almost  microscopic,  particles  are  inhaled  and 
come  in  contact  with  the  delicate  walls  of  the  air-cells,  in 
which  they  are  imbedded  under  a  certain  pressure.  "When 
any  part  is  subject  to  pressure,  it  is  well  known  that  it  gives 
way  by  absorption,  the  pressure  facilitating  the  removal  of 
worn-out  matter,  but  interfering  with  the  deposition  of  new 


366  RESPIRATION. 

material.  These  particles  thus  penetrate  the  lung  substance, 
from  which  they  can  never  be  removed.  They  may  find 
their  way  into  the  lymphatic  vessels,  but  become  fixed  in  the 
lymphatic  glands,  in  which  the  quantity  is  always  propor- 
tionate to  that  which  exists  in  ihe  lungs.  It  has  been  shown 
that  the  particles  introduced  under  the  skin  in  tattooing  may 
also  be  taken  up  by  the  lymphatics,  but  are  arrested  and 
fixed  in  the  glands.1 

There  is  no  ground  for  the  hypothesis  that  the  carbona- 
ceous matter  of  the  lungs  and  bronchial  glands  is  deposited 
as  a  residue  of  combustion  of  the  hydrocarbons,  in  the  process 
of  respiration. 

Movements  of  Respiration. 

In  man  and  the  warm-blooded  animals'  generally,  the 
lungs  attain  their  greatest  degree  of  development,  the  sur- 
face which  is  exposed  to  the  atmosphere  is  relatively  great- 
est, and  it  is  in  these  organs  that  nearly  all  of  the  process  of 
interchange  of  gases  takes  place.  In  all  animals  of  this  class, 
inspiration  takes  place  as  a  consequence  of  enlargement  of 
the  thoracic  cavity,  and  the  entrance  of  a  quantity  of  air 
through  the  respiratory  passages  corresponding  to  the  in- 
creased capacity  of  the  lungs.  In  the  mammalia,  the  chest  is 
enlarged  by  the  action  of  muscles;  and  in  ordinary  respi- 
ration, inspiration  is  an  active  process,  while  expiration  is 
comparatively  passive.  In  many  birds,  the  chest  is  com- 
pressed by  muscular  action  in  expiration,  and  inspiration  is 
effected  in  a  measure  by  elastic  ligaments.  In  both  classes, 
the  air  is  drawn  into  the  chest  to  supply  the  space  produced 
by  its  enlargement.  In  some  of  the  lower  orders  of  animals 
which  have  no  ribs  or  sternum,  or  in  which  the  thorax  is 
immovable  and  there  exists  no  division  between  its  cavity 
and  the  abdomen,  the  air  is  forced  into  the  lungs  by  an  act 
like  deglutition.  In  these  animals  (frogs,  lizards,  turtles, 

1  The  results  of  the  investigations  of  Kobin  are  to  be  found  in  the  Chimic 
Anatomique,  by  ROBIN  and  YERDEIL,  tome  iii.,  p.  505  et  seq. 


INSPIRATION.  367 

etc.)  the  respiratory  acts  are  very  infrequent ;  and  in  some, 
the  oxidation  of  the  blood  is  more  effectually  performed  by 
the  general  surface  than  by  the  lungs. 

A  glance  at  the  physiological  anatomy  of  the  thorax  in 
the  human  subject  makes  it  evident  that  the  action  of  certain 
muscles  will  considerably  increase  its  capacity.  In  the  first 
place,  the  diaphragm  mounts  up  into  its  cavity  in  the  form 
of  a  vaulted  arch.  By  contraction  of  its  fibres,  it  is  brought 
nearer  a  plane,  and  thus  the  vertical  diameter  of  the  thorax 
is  increased.  The  walls  of  the  thorax  are  formed  by  the 
dorsal  vertebrae  and  ribs  posteriorly,  by  the  upper  ten  ribs 
laterally,  and  by  the  sternum  and  costal  cartilages  anteriorly. 
The  direction  of  the  ribs,  their  mode  of  connection  with  the 
sternum  by  the  costal  cartilages,  and  their  articulation  with 
the  vertebral  column,  are  such  that  by  their  movements  the 
antero-posterior  and  transverse  diameters  of  the  chest  may  be 
considerably  modified. 

Inspiration. 

The  ribs  are  somewhat  twisted  upon  themselves,  and  have 
a  general  direction  forwards  and  downwards.  The  first 
rib  is  nearly  horizontal,  but  the  obliquity  progressive- 
ly increases  from  the  upper  to  the  lower  parts  of  the 
chest.  They  are  articulated  with  the  bodies  of  the  vertebrae, 
so  as  to  allow  of  considerable  motion.  The  upper  seven  ribs 
are  attached  by  the  costal  cartilages  to  the  sternum,  these 
cartilages  running  upwards  and  inwards.  The  cartilages  of 
the  eighth,  ninth,  and  tenth  ribs  are  joined  to  the  cartilage 
of  the  seventh.  The  eleventh  and  twelfth  are  floating  ribs, 
and  are  only  attached  to  the  vertebrae. 

It  may  be  stated  in  general  terms  that  inspiration  is  effect- 
ed by  descent  of  the  diaphragm  and  elevation  of  the  ribs ; 
and  expiration  by  elevation  of  the  diaphragm  and  descent 
of  the  ribs. 

Arising  severally  from  the  lower  border  of  each  rib,  and 


368  RESPIRATION. 

attached  to  the  upper  border  of  the  rib  below,  are  the  eleven  ex- 
ternal intercostal  muscles,  the  fibres  of  which  have  an  oblique 
direction  from  above  downwards  and  forwards.  Attached  to 
the  inner  borders  of  the  ribs  are  the  internal  intercostals,  which 
have  a  direction  from  above  Downwards  and  backwards,  at 
right  angles  to  the  fibres  of  the  external  intercostals.  There 
are  also  a  number  of  muscles  attached  to  the  thorax  and  spine, 
thorax  and  head,  upper  part  of  humerus,  etc.,  which  are 
capable  of  elevating  either  the  entire  chest  or  the  ribs. 
These  must  act  as  muscles  of  inspiration  when  the  attach- 
ments to  the  thorax  become  the  movable  points.  Some  of 
them  are  called  into  action  during  ordinary  respiration; 
others  act  as  auxiliaries  when  respiration  is  a  little  exagger- 
ated, as  after  exercise,  and  are  called  ordinary  auxiliaries ; 
while  others,  which  ordinarily  have  a  different  function, 
are  only  brought  into  play  when  respiration  is  excessively 
difficult,  and  are  called  extraordinary  auxiliaries. 

The  following  are  the  principal  muscles  concerned  in  in- 
spiration : 

Muscles  of  Inspiration. 

ORDINARY  RESPIRATION. 

Muscle.  Attachments. 

Diaphragm Circumference  of  lower  border  of  thorax. 

Scalenus  Anticus Transverse  processes  of  third,  fourth, 

fifth,  and  sixth  cervical  vertebrae 

tubercle  of  first  rib. 

Scalenus  Medius Transverse  processes  of  six  lower  cervi- 
cal vertebrae upper  surface  of  first 

rib. 

Scalenus  Posticus Transverse  processes  of  lower  two  or 

three  cervical  vertebras outer  sur- 
face of  second  rib. 

External  Intercostals Outer  borders  of  the  ribs. 

Sternal  portion  of  Internal  Intercostals .  .Borders  of  the  costal  cartilages. 

Twelve  Levatores  Costarum Transverse  processes  of  dorsal  vertebrae 

ribs,  between  the  tubercles  and 

angles. 


ACTION   OF  THE  DIAPHRAGM.  369 


Ordinary  Auxiliaries. 

Muscle.  Attachments. 

Serratus  Posticus  Superior Ligaraentum  nuchae,  spinous  processes 

of  last  cervival  and  upper  two  or  threo 

dorsal  vertebrae upper  borders  of 

second,  third,  fourth,  and  fifth  ribs 
just  beyond  the  angles. 

Stemo-mastoideus Upper  part  of  sternum mastoid  pro- 
cess of  temporal  bone. 

Extraordinary  Auxiliaries. 

Levator  Anguli  Scapulse .Transverse  processes  of  upper  three  or 

four  cervical  vertebrae posterior 

border  of  superior  angle  of  the  scapula. 

Trapezius  (superior  portion) Ligamentum  nuchse  and  seventh  cervical 

vertebra the  upper  border  of  the 

spine  of  the  scapula. 

Pectoralis  Minor Coracoid  process  of  scapula anterior 

surface  and  upper  margins  of  third, 
fourth,  and  fifth  ribs  near  the  cartilages. 

Pectoralis  Major  (inferior  portion) Bicipital  groove  of  humerus costal 

cartilages  and  lower  part  of  the  ster- 
num. 

Serratus  Magnus Inner  margin  of  posterior  border  of  scap- 
ula——external  surface  and  upper  bor- 
der of  upper  eight  ribs. 

Action  of  the  Diaphragm. — The  descriptive  and  general 
anatomy  of  the  diaphragm  gives  a  pretty  correct  idea  of  its 
functions  in  respiration.  It  arises,  anteriorly,  from  the  inner 
surface  of  the  ensiform  cartilage,  laterally,  from  the  inner 
surface  of  the  lower  borders  of  the  costal  cartilages  and  the 
six  or  seven  inferior  ribs,  passes  over  the  quadratus  lumborum 
by  the  external  arcuate  ligament,  and  the  psoas  magnus  by 
the  internal  arcuate  ligament,  and  has  two  tendinous  slips  of 
origin,  called  crurse  of  the  diaphragm,  from  the  bodies  of  the 
second,  third,  and  fourth  lumbar  vertebrae  and  the  interverte- 
bral  cartilages  on  the  right  side,  and  the  second  and  third  lum- 
bar vertebrae  and  the  intervertebral  cartilages  on  the  left  side. 
From  this  origin,  which  extends  around  the  lower  circumfer- 
24 


370  RESPIRATION. 

ence  of  the  thorax,  it  mounts  up  into  the  cavity  of  the  chest, 
forming  a  vaulted  arch  or  dome,  with  its  concavity  toward 
the  abdomen  and  its  convexity  toward  the  lungs.  In  the  cen  - 
tral  portion  there  is  a  tendon  of  considerable  size,  and  shaped 
something  like  the  club  on  a^  playing  card,  with  middle, 
right,  and  left  leaflets.  The  remainder  of  the  organ  is  com- 
posed of  radiating  fibres  of  the  striped  or  voluntary  muscular 
tissue.  The  oesophagus,  aorta,  and  inferior  vena  cava  pass 
through  the  diaphragm  from  the  thoracic  to  the  abdominal 
cavity,  by  three  openings. 

The  opening  for  the  oesophagus  is  surrounded  by  muscular 
fibres,  by  which  it  is  partially  closed  when  the  diaphragm 
contracts  in  inspiration,  as  the  fibres  simply  surround  the 
tube,  and  none  are  attached  to  it. 

The  orifice  for  the  aorta  is  bounded  by  the  bone  and 
aponeurosis  posteriorly,  and  in  front  by  a  fibrous  band  to 
which  the  muscular  fibres  are  attached;  so  that  their  con- 
traction has  rather  a  tendency  to  increase,  than  diminish,  the 
caliber  of  the  vessel. 

The  orifice  for  the  vena  cava  is  surrounded  entirely  by 
tendinous  structure,  and  contraction  of  the  diaphragm,  though 
it  might  render  the  form  of  the  orifice  more  nearly  circular, 
can  have  no  effect  upon  its  caliber. 

The  action  of  the  diaphragm  can  be  easily  studied  in  the 
inferior  animals  by  vivisections.  If  the  abdomen  of  a  cat, 
which,  from  the  conformation  of  the  parts,  is  well  adapted  to 
this  experiment,  be  largely  opened,  we  can  observe  the  descent 
of  the  tendinous  portion,  and  the  contraction  of  the  muscular 
fibres.  The  action  of  this  muscle  may  be  rendered  more 
apparent  by  compressing  the  walls  of  the  chest  with  the  hands, 
so  as  to  interfere  somewhat  with  the  movements  of  the  ribs. 
In  ordinary  respiration,  the  'descent  of  the  diaphragm  and 
its  approximation  to  a  plane  is  the  chief  phenomenon  ob- 
served; but. as  there  is  a  slight  resistance  to  the  depres- 
sion of  the  central  tendon,  it  is  probable  that  there  is  also  a 
slight  elevation  of  the  inferior  ribs,  the  diaphragm  assisting, 


ACTION  OF  THE  DIAPHKAGM.  371 

in  a  limited  degree  it  is  true,  the  action  of  the  external 
intercostals. 

The  phenomena  referable  to  the  abdomen,  which  coincide 
with  the  descent  of  the  diaphragm,  can  easily  be  observed 
in  the  human  subject.  As  the  diaphragm  is  depressed, 
it  necessarily  pushes  the  viscera  before  it,  and  inspiration 
is  therefore  accompanied  by  protrusion  of  the  abdomen. 
This  may  be  rendered  very  marked  by  a  forced  or  deep  in- 
spiration. 

The  action  of  the  diaphragm  maybe  illustrated  by  a  very 
simple  yet  striking  experiment.  In  an  animal  just  killed, 
after  opening  the  abdomen,  if  we  take  hold  of  the  structures 
which  are  attached  to  the  central  tendon,  and  make  traction, 
we  imitate,  in  a  rough  way,  the  movements  of  the  diaphragm 
in  respiration,  and  the  air  will  pass  into  the  lungs,  sometimes 
with  a  distinctly  audible  sound. 

The  effects  of  the  action  of  the  diaphragm  upon  the  size 
of  its  orifices  are  chiefly  limited  to  the  oesophageal  opening. 
The  anatomy  of  the  parts  is  such  that  contraction  of  the 
muscular  fibres  has  a  tendency  to  close  this  orifice.  When 
we  come  to  treat  of  the  digestive  system,  we  shall  see  that  this 
is  auxiliary  to  the  action  of  the  muscular  walls  of  the  oeso- 
phagus itself,  by  which  the  cardiac  opening  of  the  stomach 
is  regularly  closed  during  inspiration.  This  may  become 
important  when  the  stomach  is  much  distended ;  for  descent 
of  the  diaphragm  compresses  all  the  abdominal  organs,  and 
might  otherwise  cause  regurgitation  of  a  portion  of  its  con- 
tents. 

The  contractions  of  the  diaphragm  are  animated  almost 
exclusively,  if  not  exclusively,  by  the  phrenic  nerve ;  a  nerve 
which,  having  the  office  of  supplying  the  most  important 
respiratory  muscle,  derives  its  filaments  from  a  number  of 
sources.  It  arises  from  the  third  and  fourth  cervical  nerves, 
receiving  a  branch  from  the  fifth,  and  sometimes  from  the 
sixth ;  it  passes  through  the  chest,  penetrates  the  diaphragm, 
and  is  distributed  to  its  under  surface.  This  nerve  was  the 


372  RESPIRATION. 

subject  of  numerous  experiments  by  the  earlier  physiologists, 
who  were  greatly  interested  in  the  minutiaa  of  the  action  of 
the  diaphragm,  and  other  muscles,  in  respiration.  Its  gal- 
vanization produces  convulsive  contractions  of  the  diaphragm, 
and  its  section  paralyzes  the  muscle  almost  completely.  It 
was  noticed  by  Lower,  that  after  section  of  both  phrenic 
nerves  the  movements  of  the  abdomen  were  reversed,  and  it 
became  retracted  in  inspiration.1  This  is  explained  and  illus- 
trated by  voluntary  suspension  of  the  action  of  the  diaphragm, 
and  exaggeration  of  the  costal  movements.  As  the  ribs  are 
raised,  the  atmospheric  pressure  causes  the  diaphragm  to 
mount  up  into  the  cavity  of  the  thorax,  and  of  course  the 
abdominal  organs  follow. 

From  the  great  increase  in  the  capacity  of  the  chest  pro- 
duced by  the  action  of  the  diaphragm,  and  its  constant  and 
universal  action  in  respiration,  it  must  be  regarded  as  by  far 
the  most  important  and  efficient  of  the  muscles  of  inspiration. 

Hiccough,  sobbing,  laughing,  and  crying  are  produced 
mainly  by  the  action  of  the  diaphragm,  particularly  hic- 
cough and  sobbing,  which  are  produced  by  spasmodic  con- 
tractions of  this  muscle,  generally  beyond  the  control  of  the 
will. 

Action  of  the  Muscles  which  elevate  the  JRibs. — /Scalene 
Muscles. — In  ordinary  respiration,  the  ribs  and  the  entire 
chest  are  elevated  by  the  combined  action  of  a  number  of 
muscles.  The  three  scalene  muscles  are  attached  to  the  cervi- 
cal vertebrae  and  the  first  and  second  ribs.  These  muscles, 
which  act  particularly  upon  the  first  rib,  must  elevate  with 
it,  in  inspiration,  the  rest  of  the  thorax.  The  articulation  of 
the  first  rib  with  the  vertebral  column  is  very  movable,  but 
it  is  joined  to  the  sternum  by  a  very  short  cartilage,  whicli 
allows  of  very  little  movement,  so  that  its  elevation  necessa- 
rily carries  with  it  the  sternum.  This  movement  increases 
both  the  transverse  and  antero-posterior  diameters  of  the 

1  BERARD,  Cours  de  Physiologic,  Paris,  1851,  tome  iii.,  p.  245. 


ACTION  OF  THE   SCALENI.  373 

thorax,  from  the  mode  of  articulation  and  direction  of  the 
ribs,  which  are  somewhat  rotated  as  well  as  rendered  more 
horizontal. 

Perhaps  there  is  no  set  of  muscular  actions  to  which  as 
much  observation  and  speculation  have  been  devoted  as  those 
concerned  in  respiration ;  and  the  actions  of  the  muscles 
which  are  attached  to  the  thorax  are  so  complex  and  difficult 
of  observation,  that  the  views  of  physiologists  concerning 
them  are  still  somewhat  conflicting.  While  some  adopt  the 
opinion  of  Haller,1  that  the  first  rib  is  almost  fixed  and  im- 
movable, others  contend,  as  did  Magendie,  that  it  is  the 
most  movable  of  all.2  With  regard  to  this  point  there  can 
now,  it  seems,  be  no  doubt.  By  putting  the  thumb  and  fin- 
ger on  either  side  of  thp  neck  over  the  scaleni,  we  can  dis- 
tinctly feel  these  muscles  contract  with  every  tolerably  deep 
inspiration  (a  movement  which  Magendie  proposed  to  call 
the  respiratory  pulse,  loo.  tit.) ;  and  it  is  further  evident 
that  though  in  the  male,  in  ordinary  respiration,  the  sternum 
is  almost  motionless,  in  the  female,  and  in  the  male,  in  deep 
inspirations,  the  sternum  is  considerably  elevated  and  pro- 
jected, particularly  at  its  lower  part.  This  latter  movement 
increases  the  antero-posterior  diameter  of  the  thorax,  and  can 
be  measured  with  an  appropriate  instrument.  The  elevation 
of  the  sternum  is  necessitated  by  its  close  and  almost  im- 
movable connection,  through  its  short  cartilage,  with  the 
first  rib. 

The  action  of  the  scaleni,  while  it  is  inconsiderable  in 
ordinary  respiration  in  the  male,  in  all  cases  renders  the  first 
rib  practically  a  fixed  point,  from  which  those  intercostal 
muscles  which  raise  the  ribs  can  act. 

Intercostal  Muscles. — Concerning  the  mechanism  of  the 
action  of  these  muscles,  there  is  great  difference  of  opinion 
among  physiologists ;  so  much,  indeed,  that  the  author  of  a 

1  Elementa  Physiologies,  Lausanne,  1761,  tomus  iii.,  p.  23. 

2  Precis  filementaire  de  Physiologic,  tome  ii.,  p.  317. 


374  RESPIRATION. 

late  elaborate  work  assumes  that  the  question  is  still  left  in 
considerable  uncertainty.1  The  most  elaborate  researches  on 
this  point  are  those  of  Beau  and  Maissiat  (Archives  Generates 
de  Medecine,  1843),  and  Sibson  (Philosophical  Transactions, 
1846).  The  latter  seem  to  settle  the  question  of  the  mode  of 
action  of  the  intercostals,  and  explain  satisfactorily  certain 
points  which  even  now  are  not  generally  appreciated.2 

Let  us  first  note  the  changes  which  take  place  in  the 
direction  of  the  ribs,  and  their  relation  to  each  other,  in 
inspiration,  before  considering  the  way  in  which  these  move- 
ments are  produced. 

In  the  dorsal  region,  the  spinal  column  forms  an  arch 
with  its  concavity  toward  the  chest,  and  the  ribs  increase  in 
length  progressively,  from  above  downwards,  to  the  deepest 
portion  of  the  arch,  where  they  are  longest,  and  then  become 
progressively  shorter.  "  During  inspiration  the  ribs  approach 
to  or  recede  from  each  other  according  to  the  part  of  the  arch 
with  which  they  articulate ;  the  four  superior  ribs  approach 
each  other  anteriorly  and  recede  from  each  other  posteriorly ; 
the  fourth  and  fifth  'ribs,  and  the  intermediate  set  (sixth, 
seventh,  and  eighth),  move  further  apart  to  a  moderate,  the 
diaphragmatic  set  (four  inferior),  to  a  great  extent.  The  upper 
edge  of  each  of  these  ribs  glides  toward  the  vertebrae  in  rela- 
tion to  the  lower  edge  of  the  rib  above,  with  the  exception  of 
the  lowest  rib,  which  is  stationary." 3 

These  movements,  accurately  and  admirably  described 
by  Sibson,  and  illustrated  by  drawings  of  the  chest,  empty, 

1  LONGET,  Traite  de  Physiologic,  Paris,  1861,  tome  i.,  p.  629. 

a  Sibson's  article  is  the  most  complete  ever  published  upon  the  mechanism  of 
respiration.  The  action  of  the  respiratory  muscles  was  observed  in  vivisections, 
and  the  mechanism  by  which  the  capacity  of  the  thorax  is  modified  is  illustrated 
in  the  most  ingenious  manner  by  mechanical  contrivances,  representing  the  posi- 
tion, etc.,  of  the  ribs,  and  their  movements.  By  dilating  the  chest  after  death, 
also,  he  shows  the  change  which  takes  place  in  the  direction  of  the  ribs  and  the 
consequent  shortening  of  certain  muscles,  which,  he  assumes,  must  act  as  muscles 
of  inspiration,  a  fact  which  he  has  taken  care  to  verify  by  vivisections. 
8  SIBSON,  op.  cit.t  p.  529. 


INTEECOSTAL   MUSCLES. 


375 


Dorsal  Eegion. 
Expiration.  Inspiration. 


Anterior  Eegion  of  the  Thorax. 
Inspiration.  Expiration. 


FIG.  14. 


Inspiration. 


376  KESPIRA.TION. 

as  in  expiration,  and  distended  with  air,  increase  the  antero 
posterior  and  transverse  diameters  of  the  thorax.  As  the 
ribs  are  elevated  and  become  more  nearly  horizontal,  they 
must  push  forward  the  lower  portion  of  the  sternum.  Their 
configuration  and  mode  of  artioulation  with  the  vertebrae  are 
such,  that  they  cannot  be  elevated  without  undergoing  a  con- 
siderable rotation,  by  which  the  concavity  looking  directly 
toward  the  lungs  is  increased,  and  with  it  the  lateral  diameter 
of  the  chest.  All  the  intercostal  spaces  posteriorly  are  widen- 
ed in  inspiration. 

These  points  are  clearly  illustrated  in  the  accompanying 
diagrams.1 

The  ribs  are  elevated  by  the  action  of  the  external  inter- 
costals, the  sternal  portion  of  the  internal  intercostals,  and 
the  levatores  costarum. 

The  external  intercostals  are  situated  between  the  ribs 
only,  and  are  wanting  in  the  region  of  the  costal  cartilages. 
As  the  vertebral  extremities  of  the  ribs  are  the  pivots  on 
which  these  levers  move,  and  the  sternal  extremities  are 
movable,  the  direction  of  the  fibres  of  the  intercostals,  from 
above  downwards  and  forwards,  renders  elevation  of  the  ribs 
a  necessity  of  their  contraction ;  if  it  can  be  assumed  that  the 
first  rib  is  fixed,  or  at  least  does  not  move  downwards.  The 
scalene  muscles  elevate  the  first  rib  in  ordinary  inspiration ; 
and  in  deep  inspiration,  this  takes  place  to  such  an  extent  as 
to  palpably  carry  with  it  the  sternum  and  the  lower  ribs. 
Theoretically,  then,  the  external  intercostals  can  do  nothing 
but  render  the  ribs  more  nearly  horizontal.  The  action  of 
these  muscles  has,  however,  been  the  subject  of  considerable 
controversy,  on  theoretical  grounds.  We  shall  discuss  the 
question  chiefly  from  an  experimental  point  of  view. 

If  the  external  intercostals  be  exposed  in  a  living  animal, 
the  dog  for  example,  in  which  the  costal  type  of  respiration 
is  very  marked,  close  observation  cannot  fail  to  convince  any 
one  that  these  muscles  enter  into  action  in  inspiration.  This 

1  SIBSON,  loc.  cit 


INTEECOSTAL   MUSCLES.  377 

fact  has  been  observed  by  Sibson  and  many  other  physiolo- 
gists. If  attention  be  now  directed  to  the  sternal  portion  of 
the  internal  intercostals,  situated  between  the  costal  cartilages, 
their  fibres  having  a  direction  from  above  downwards  and 
backwards,  it  is  equally  evident  that  they  enter  into  action 
with  inspiration.  By  artificially  inflating  the  lungs  after 
death,  Sibson  confirmed  these  observations,  and  showed  that 
when  the  lungs  are  filled  with  air,  the  fibres  of  these  muscles 
are  shortened.  In  inspiration  the  ribs  are  all  separated  pos- 
teriorly ;  but  laterally  and  anteriorly,  some  are  separated  (all 
below  the  fourth),  and  some  are  approximated  (all  above  the 
fourth).  Thus  all  the  interspaces,  excepting  the  anterior  por- 
tion of  the  upper  three,  are  widened  in  inspiration.  Sibson 
lias  shown  by  inflation  of  the  chest,  that  though  the  ribs  are 
separated  from  each  other,  the  attachments  of  the  intercostals 
are  approximated.  The  ribs,  from  an  excessively  oblique 
position,  are  rendered  nearly  horizontal;  and  consequently 
the  inferior  attachments  of  the  intercostals  are  brought  nearer 
the  spinal  column,  while  the  superior  attachments  on  the 
upper  borders  of  the  ribs  are  slightly  removed  from  it.  Thus 
these  muscles  are  shortened.  If,  by  separating  and  elevating 
the  ribs,  the  muscles  are  shortened,  shortening  of  the  muscles 
will  elevate  and  separate  the  ribs.  In  the  three  superior 
interspaces,  the  constant  direction  of  the  ribs  is  nearly  hori- 
zontal, and  the  course  of  the  intercostal  fibres  is  not  as  oblique 
as  in  those  situated  between  the  lower  ribs.  These  spaces  are 
narrowed  in  inspiration.  The  muscles  between  the  costal 
cartilages  have  a  direction  opposite  to  that  of  the  external 
intercostals,  and  act  upon  the  ribs  from  the  sternum,  as  the 
others  do  from  the  spinal  column.  The  superior  interspace 
is  narrowed,  and  the  remainder  are  widened,  in  inspiration. 

The  probable  explanation  of  the  great  difference  of  opin- 
ion with  regard  to  the  action  of  the  intercostals  is  the  diffi- 
culty of  comprehending,  at  the  first  blush,  that  the  contrac- 
tion of  muscles  situated  between  the  ribs  can  separate  them 
from  each  other ;  a  phenomenon  which  is  easily  understood 


378  RESPIRATION. 

after  a  careful  consideration  of  the  relative  position  of  the 
parts. 

Xevatores  Costarum. — The  action  of  these  muscles  cannot 
be  mistaken.  They  have  imnaovable  points  of  origin,  the 
transverse  processes  of  twelve  vertebrae  from  the  last  cervical 
to  the  eleventh  dorsal,  and,  spreading  ont  like  a  fan,  are  at- 
tached to  the  upper  edges  of  the  ribs  between  the  tubercles 
and  the  angles.  In  inspiration  they  contract  and  assist  in  the 
elevation  of  the  ribs.  They  are  more  developed  in  man  than 
in  the  inferior  animals. 

Auxiliary  Muscles  of  Inspiration. — The  muscles  which 
have  just  been  considered  are  competent  to  increase  the  ca- 
pacity of  the  thorax  sufficiently  in  ordinary  respiration ;  there 
are  certain  muscles,  however,  which  are  attached  to  the  ches* 
and  the  upper  part  of  the  spinal  column,  or  upper  extremities, 
which  may  act  in  inspiration,  though  ordinarily  the  chest  is 
the  fixed  point,  and  they  move  the  head,  neck,  or  arms. 
These  muscles  are  brought  into  action  when  the  movements 
of  respiration  are  exaggerated.  When  this  exaggeration  is 
but  slight  and  physiological,  as  after  exercise,  certain  of  them 
(ordinary  auxiliaries)  act  for  a  time,  until  the  tranquillity  of 
the  movements  is  restored.  But  when  there  is  obstruction 
in  the  respiratory  passages,  or  when  respiration  is  excessively 
difficult  from  any  cause,  threatening  suffocation,  all  the 
muscles  which  can  by  any  possibility  raise  the  chest  are 
brought  into  action.  The  principal  ones  are  put  down  in  the 
table  under  the  head  of  extraordinary  auxiliaries.  Most  of 
these  muscles  can  voluntarily  be  brought  into  play  to  raise 
the  chest,  and  the  mechanism  of  their  action  can  in  this  way 
be  demonstrated. 

Serratus  Posticus  Superior. — This  muscle  arises  from  the 
ligamentum  nuchse,  the  spinous  processes  of  the  last  cervical 
and  upper  two  or  three  dorsal  vertebras,  its  fibres  passing 


AUXILIARY  MUSCLES   OF  mSPIEATION.  379 

obliquely  downwards  and  outwards,  to  be  attached  to  the 
upper  borders  of  the  second,  third,  fourth,  and  fifth  ribs  just 
beyond  their  angles.  By  reversing  its  action,  as  we  have  re- 
versed the  description  of  its  origin  and  insertions,  it  is  capable 
of  increasing  the  capacity  of  the  thorax.  Sibson  has  seen 
this  muscle  contract  in  inspiration,  in  the  dog  and  the  ass.1 

Sterno-mastoideus. — That  portion  of  the  muscle  which  is 
attached  to  the  mastoid  process  of  the  temporal  bone  and  the 
sternum,  when  the  head  is  fixed,  is  capable  of  acting  as  a 
muscle  of  inspiration.  It  does  not  act  in  ordinary  respira- 
tion, but  its  contractions  can  be  readily  observed  whenever 
respiration  is  hurried  or  exaggerated. 

The  following  muscles,  as  a  rule,  only  act  as  muscles  of 
inspiration  when  respiration  is  exceedingly  difficult  or  la- 
bored. In  certain  cases  of  capillary  bronchitis,  for  example, 
the  anxious  expression  of  the  countenance  betrays  the  sense 
of  impending  suffocation ;  the  head  is  thrown  back  and  fixed, 
the  shoulders  are  braced,  and  every  available  muscle  is 
brought  into  action  to  raise  the  walls  of  the  thorax.2 

Levator  Anguli  Scapulae  and  Superior  Portion  of  the 
Trapezius. — Movements  of  the  scapula  have  often  been  ob- 
served in  very  labored  respiration.  Its  elevation  during  in- 
spiration is  chiefly  effected  by  the  levator  angnli  scapulae 
and  the  upper  portion  of  the  trapezius.  The  former  arises 
from  the  transverse  processes  of  the  upper  three  or  four  cer- 
vical vertebrae,  and  is  inserted  into  the  posterior  border  of 
the  scapula  below  the  angle.  It  is  a  thick  flat  muscle,  and 
when  the  neck  is  the  fixed  point,  assists  in  the  elevation  of 
the  thorax  by  raising  the  scapula.  The  trapezius  is  a  broad 
flat  muscle  arising  from  the  occipital  protuberance,  part  of 
the  superior  curved  line  of  the  occipital  bone,  the  ligamentum 

1  Op.  tit.,  p.  521. 

2  Under  these  circumstances,  some  muscles  which  we  have  not  thought  it  ne- 
cessary to  enumerate  may  act  indirectly  as  muscles  of  inspiration. 


380  RESPIRATION. 

michae,  and  the  spinous  processes  of  the  last  cervical  and  all 
the  dorsal  vertebrae,  to  be  inserted  into  the  upper  border  of 
the  spine  of  the  scapula.  Acting  from  its  attachments  to  the 
occiput,  the  ligamentum  nuchse,  the  last  cervical  vertebra, 
and  perhaps  one  or  two  of  the.  dorsal  vertebrae,  this  muscle 
may  elevate  the  scapula  and  assist  in  inspiration. 

Pectoralls  Minor  and  Inferior  Portion  of  the  Pectoralis 
Major. — These  muscles  act  together  to  raise  the  ribs  in  diffi- 
cult respiration.  The  pectoralis  minor  is  the  more  efficient. 
Tracing  it  from  its  attachment  to  the  coracoid  process  of  the 
scapula,  its  fibres  pass  downwards  and  forwards  to  be  attached 
by  three  indigitations  to  the  external  surface  and  upper  mar- 
gins of  the  third,  fourth,  and  fifth  ribs,  just  posterior  to  the 
cartilages.  With  the  coracoid  process  as  the  fixed  point,  this 
muscle  is  capable  of  powerfully  assisting  in  the  elevation  of 
the  ribs.  That  portion  of  the  pectoralis  major  which  is  at- 
tached to  the  lower  part  of  the  sternum  and  costal  cartilages 
is  capable  of  acting  from  its  insertion  into  the  bicipital 
groove  of  the  humerus,  when  the  shoulders  are  fixed,  in  con- 
cert with  the  pectoralis  minor.  In  great  dyspnoea,  it  is  fre- 
quently observed  that  the  shoulders  are  braced,  the  pectorals 
acting  most  vigorously  to  raise  the  walls  of  the  chest. 

Serratus  Magnus. — This  is  a  broad  thin  muscle  covering  a 
great  portion  of  the  lateral  walls  of  the  thorax.  Attached  to  the 
inner  margin  of  the  posterior  border  of  the  scapula,  its  fibres 
pass  forwards  and  downwards,  and  are  attached  to  the  exter- 
nal surface  and  upper  borders  of  the  eight  superior  ribs. 
Acting  from  the  scapula,  this  muscle  is  capable  of  assisting 
the  pectorals  in  raising  the  ribs,  and  becomes  a  powerful  aux- 
iliary in  difficult  inspiration. 

We  have  thus  considered  the  functions  of  the  principal 
inspiratory  muscles,  without  taking  up  those  which  have  an 
insignificant  or  undetermined  action.  In  many  animals  the 
nares  are  considerably  distended  in  inspiration;  and  in  the 


AUXILIARY  MUSCLES   OF  INSPIRATION.  381 

horse,  winch  does  not  respire  by  the  mouth,  these  movements 
are  as  essential  to  life  as  are  the  respiratory  movements  of  the 
larynx.  In  man,  as  a  rule,  the  nares  undergo  no  movement 
unless  respiration  be  somewhat  exaggerated.  In  very  diffi- 
cult respiration  the  mouth  is  opened  at  each  inspiratory  act. 
"We  have  not  thought  it  necessary  to  treat  of  the  action  of 
those  muscles  which  serve  to  fix  the  head,  neck,  or  shoulders 
in  dyspnoea. 

The  division  into  muscles  of  ordinary  inspiration,  ordi- 
nary auxiliaries,  and  extraordinary  auxiliaries,  must  not  be 
taken  as  absolute.  In  the  male,  in  ordinary  respiration,  the 
diaphragm,  intercostals,  and  levatores  costarum  are  the  great 
inspiratory  muscles,  and  the  action  of  the  scaleni,  with  the 
consequent  elevation  of  the  sternum,  is  commonly  very  slight, 
or  perhaps  wanting.  In  the  female,  the  movements  of  the 
upper  parts  of  the  chest  are  very  marked,  and  the  scaleni,  the 
serratus  posticus  superior,  and  sometimes  the  sterno-mastoid, 
are  brought  into  action  in  ordinary  respiration.  In  the  vari- 
ous types  of  respiration,  the  action  of  the  muscles  engaged  in 
ordinary  respiration  necessarily  presents  considerable  varia- 
tions. 


CHAPTER  XI. 

MOVEMENTS    OF    EXPIRATION. 

Influence  of  the  elasticity  of  the  pulmonary  structure  and  walls  of  the  chest—- 
Muscles of  expiration — Internal  intercostals — Infra-costales — Triangularis  ster- 
ni — Action  of  the  abdominal  muscles  in  expiration — Types  of  respiration — 
Abdominal  type — Inferior  costal  type — Superior  costal  type — Frequency  of  the 
respiratory  movements — Relations  of  inspiration  and  expiration  to  each  other — 
The  respiratory  sounds — Coughing — Sneezing — Sighing — Yawning — Laugh- 
ing— Sobbing — Hiccough — Capacity  of  the  lungs  and  the  quantity  of  air 
changed  in  the  respiratory  acts — Residual  air — Reserve  air — Tidal,  or  breathing 
air — Complemental  air — Extreme  breathing  capacity — Relations  in  volume  of 
the  expired  to  the  inspired  air — Diffusion  of  air  in  the  lungs. 

THE  air  is  expelled  from  the  lungs,  in  ordinary  expiration, 
by  a  simple  and  comparatively  passive  process.  The  lungs 
contain  a  great  number  of  elastic  fibres  surrounding  the  air- 
cells  and  the  smallest  ramifications  of  the  bronchial  tubes, 
which  give  them  great  elasticity.  "We  can  form  an  idea  of 
the  extent  of  elasticity  of  these  organs,  by  simply  removing 
them  from  the  chest,  when  they  collapse  and  become  many 
times  smaller  than  the  cavity  which  they  before  completely 
filled.  The  thoracic  walls  are  also  very  elastic,  particularly 
in  young  persons.  After  the  muscles  which  increase  the 
capacity  of  the  thorax  cease  their  action,  the  elasticity  of  the 
costal  cartilages  and  the  tonicity  of  muscles  which  have  been 
put  on  the  stretch,  will  restore  the  chest  to  what  we  may  call 
its  passive  dimensions.  This  elasticity  is  likewise  capable  of 
acting  as  an  inspiratory  force  when  the  chest  has  been  com- 


EXPIRATION.  383 

pressed  in  any  way.  There  are  also  certain  muscles,  the 
action  of  which  is  to  draw  the  ribs  downward,  and  which,  in 
tranquil  respiration,  are  antagonistic  to  those  which  elevate 
the  ribs.  Aside  from  this,  many  operations,  such  as  speak- 
ing, blowing,  singing,  etc.,  require  powerful,  prolonged,  or 
complicated  acts  of  expiration,  in  which  numerous  muscles 
are  brought  into  play. 

Expiration  may  be  considered  as  depending  upon  two 
causes : 

1.  The  passive  influence  of  the  elasticity  of  the  lungs  and 
the  thoracic  walls. 

2.  The  action  of  certain  muscles,  which  either  diminish 
the  transverse  and  antero-posterior  diameters  of  the  chest  by 
depressing  the  ribs  and  sternum,  or  the  vertical  diameter  by 
pressing  up  the  abdominal  viscera  behind  the  diaphragm. 

Influence  of  the  Elasticity  of  the  Pulmonary  Structure 
and  Walls  of  the  Chest. — It  is  easy  to  understand  the  in- 
fluence of  the  elasticity  of  the  pulmonary  structure  in  expi- 
ration. From  the  collapse  of  the  lungs  when  openings  are 
made  in  the  chest,  it  is  seen  that  even  after  the  most  complete 
expiration,  these  organs  have  a  tendency  to  expel  part  of  their 
gaseous  contents,  which  cannot  be  fully  satisfied  until  the 
chest  is  opened.  They  remain  partially  distended,  from  the 
impossibility  of  collapse  of  the  thoracic  walls  beyond  a  certain 
point ;  and  by  virtue  of  their  elasticity,  they  exert  a  suction 
force  upon  the  floor  of  the  thorax,  the  diaphragm,  causing  it 
to  form  a  vaulted  arch  or  dome  above  the  level  of  the  lower 
circumference  of  the  chest.  When  the  lungs  are  collapsed, 
the  diaphragm  hangs  loosely  between  the  abdominal  and 
thoracic  cavities.  In  inspiration  and  in  expiration,  then,  the 
relations  between  the  lungs  and  diaphragm  are  reversed.  In 
inspiration,  the  descending  diaphragm  exerts  a  suction  force 
on  the  lungs,  drawing  them  down ;  in  expiration,  the  elastic 
lungs  exert  a  suction  force  upon  the  diaphragm  drawing  it 
up.  This  antagonism  is  one  of  the  causes  of  the  great  power 


384  RESPIRATION. 

of  the  diaphragm  as  an  inspiratoiy  muscle.  Carson,  in  1820,1 
was  the  first  to  note  the  relation  of  the  elasticity  of  the  lungs 
to  the  expulsion  of  air.  Introducing  a  IT  tube  partly  filled 
with  water  into  the  trachea  of  an  animal  just  killed,  and 
securing  it  by  a  ligature,  this  ^bserver  noted  a  considerable 
pressure  on  opening  the  chest ;  equal  in  the  calf,  sheep,  or 
dog  to  a  column  of  water  of  from  12  to  18  inches,  and  in  the 
cat  or  rabbit,  from  6  to  10  inches.2 

The  elasticity  of  the  lungs  operates  chiefly  upon  the  dia- 
phragm in  reducing  the  capacity  of  the  chest ;  for  the  walls 
of  the  thorax,  by  virtue  of  their  own  elasticity,  have  a  reac- 
tion which  succeeds  the  movements  produced  by  the  inspi- 
ratory  muscles.  A  simple  experiment,  which  we  have  often 
performed  in  public  demonstrations,  illustrates  the  chief  ex- 
piratory influence  of  the  elasticity  of  the  lungs.  If,  in  an 
animal  just  killed,  we  open  the  abdomen,  seize  hold  of  the 
vena  cava  as  it  passes  through  the  diaphragm,  and  make 
traction,  we  imitate  the  action  of  this  muscle  sufficiently  to 
produce  at  times  an  audible  inspiration ;  on  loosing  our  hold, 
we  have  expiration,  as  it  is  in  a  measure  accomplished  in 
natural  respiration,  by  virtue  of  the  resiliency  of  the  lungs, 
carrying  the  diaphragm  up  into  the  thorax. 

Though  this  is  the  main  action  of  the  lungs  themselves 
in  expiration,  their  relations  to  the  walls  of  the  thorax  are 
important.  By  virtue  of  their  elasticity,  they  assist  the  pas- 
sive collapse  of  the  chest.  When  they  lose  this  property  to 
any  considerable  extent,  as  in  vesicular  emphysema,  they 
offer  a  notable  resistance  to  the  contraction  of  the  thorax ;  so 
much,  indeed,  that  in  old  cases  of  this  disease  the  movements 
are  much  restricted,  and  the  chest  presents  a  characteristic 

1  Philosophical  Transactions,  1820. 

2  If,  after  noting  the  elevation  in  the  liquid  due  to  the  elasticity  of  the  lungs, 
these  organs  be  stimulated  by  means  of  a  current  of  galvanism,  the  liquid  will 
gradually  rise,  in  obedience  to  the  contractions  of  the  muscular  elements  of  the 
bronchial  tubes.     This  slow  contraction,  characteristic  of  the  non-striated  muscu- 
lar fibres,  does  not  intervene  in  the  physiological  phenomena  of  expiration,  but 
the  action  of  these  fibres  is  important  in  certain  cases  of  disease. 


EXPIRATION.  385 

rounded  and  distended  appearance.  In  some  of  these  cases 
the  elasticity  of  the  lungs  is  so  far  lost,  that  when  the  chest 
is  opened  after  death,  they  are  actually  protruded,  instead  of 
collapsed.1 

Little  more  need  be  said  concerning  the  passive  move- 
ments of  the  thoracic  walls.  When  the  action  of  the  inspi- 
ratory  muscles  ceases,  the  ribs  regain  their  oblique  direction, 
the  intercostal  spaces  are  narrowed,  and  the  sternum,  if  it 
have  been  elevated  and  drawn  forward,  falls  back  to  its  place 
by  the  simple  elasticity  of  the  parts. 

Action  of  Muscles  in  Expiration. — The  following  are  the 
principal  muscles  concerned  in  expiration  : 


Muscles  of  Expiration. 

ORDINAEY   RESPIRATION. 

Muscle.  Attachments. 

Osseous  portion  of  Internal  Intercostals.  .Inner  borders  of  the  ribs. 

Infra-costales Inner  surfaces  of  the  ribs. 

Triangularis  Sterni Ensiform  cartilage,  lower  borders  of 

sternum,  lower  three  or  four  costal 

cartilages cartilages  of  the  second, 

third,  fourth,  and  fifth  ribs. 

1  In  old  cases  of  emphysema,  the  chest  generally  becomes  rounded  and  dis- 
tended, presenting  constantly  the  appearance  which  it  has  in  forced  inspiration. 
This  is  explained  in  the  following  way :  Emphysema  is  generally  preceded  and 
accompanied  by  a  difficulty  in  respiration,  from  some  cause  which  is  more  or  less 
constant.  This  gives  rise  to  frequent  violent  movements  of  inspiration,  when  the 
lungs  and  chest  are  distended  to  their  utmost  capacity.  In  this  condition,  expi- 
ration is  difficult,  and  the  chest  collapses  but  imperfectly.  Gradually,  as  the  per- 
manent dilatation  of  the  air-cells  gains  ground,  the  lungs  lose  their  elasticity,  and 
offer  considerable  resistance  to  the  collapse  of  the  thoracic  walls.  But  difficult 
breathing,  and  consequent  violent  elevation  of  the  ribs,  becomes  more  and  more 
frequent;  the  chest  is  constantly  dilated,  the  lungs  following,  of  course,  but  refus- 
ing to  collapse  in  expiration,  until  the  chest  becomes  permanently  distended.  In 
this  condition,  the  lungs  press  downward,  as  well  as  laterally,  and  the  movements 
of  the  diaphragm  are  considerably  restricted. 
25 


386  RESPIRATION. 


Auxiliaries. 

Attachments. 

Obliquus  Externus External  surface  and  inferior  borders  of 

eight  inferior  ribs the  anterior 

Half  of  the  crest  of  the  ileum,  Pou- 
part's  ligament,  linea  alba. 

Obliquus  Internus Outer  half  of  Poupart's  ligament,  ante- 
rior two-thirds  of  the  crest  of  the 

ileum,  lumbar  fascia cartilages  of 

four  inferior  ribs,  lineal  alba,  crest  of 
the  pubis,  pectineal  line. 

Transversalis Outer  third  of  Poupart's  ligament,  ante- 
rior two-thirds  of  the  crest  of  the 
ileum,  lumbar  vertebrae,  inner  sur- 
face of  cartilages  of  six  inferior  ribs 

crest  of  the  pubis,  pectineal  line, 

linea  alba. 

Sacro-lumbalis Sacrum angles  of  the  six  inferior 

ribs. 

Internal  Intercostals. — The  internal  intercostals  have  dif- 
ferent functions  in  different  parts  of  the  thorax.  They  are 
attached  to  the  inner  borders  of  the  ribs  and  costal  cartilages. 
Between  the  ribs  they  are  covered  by  the  external  intercos- 
tals, but  .between  the  costal  cartilages  are  simply  covered 
by  aponeurosis.  Their  direction  is  from  above  downwards 
and  backwards,  at  right  angles  to  the  external  intercostals. 
The  function  of  that  portion  of  the  internal  intercostals  situ- 
ated between  the  costal  cartilages  has  already  been  noted. 
They  assist  the  external  intercostals  in  elevating  the  ribs  in 
inspiration.  Between  the  ribs  these  muscles  are  directly  an- 
tagonistic to  the  external  intercostals.  They  are  more  nearly 
at  right  angles  to  the  ribs,  particularly  in  that  portion  of  the 
thorax  where  the  obliquity  of  the  ribs  is  greatest.  The  ob- 
servations of  Sibson  have  shown  that  they  are  elongated 
when  the  chest  is  distended,  and  shortened  when  the  chest  is 
collapsed.  This  fact,  taken  in  connection  with  experiments 
on  living  animals,  shows  that  they  are  muscles  of  expiration. 
Their  contraction  tends  to  depress  the  ribs,  and  consequentlv 


INFKA-COSTALES — TRIANGULAKIS   STEENI.  387 

to  diminisli  the  capacity  of  the  chest.  If  we  bring  an  ani- 
mal, a  dog  for  example,  completely  under  the  influence  of 
ether,  expose  the  walls  of  the  chest,  dissect  off  the  fascia  from 
some  of  the  external  intercostals,  then  remove  carefully  a 
portion  of  one  or  two  of  these  muscles  so  as  to  expose  the 
fibres  of  the  -internal  intercostals,  it  is  not  difficult,  on  close 
examination,  to  observe  the  antagonism  between  the  two  sets 
of  muscles ;  one  being  brought  into  action  in  inspiration  and 
the  other  in  expiration. 

Infra-costales. — These  muscles,  situated  at  the  posterior 
part  of  the  thorax,  are  variable  in  size  and  number.  They 
are  most  common  at  the  lower  part  of  the  chest.  Their 
fibres  arise  from  the  inner  surface  of  one  rib  to  be  inserted 
into  the  inner  surface  of  the  first,  second,  or  third  rib  below. 
The  fibres  follow  the  direction  of  the  internal  intercostals, 
and  acting  from  their  lower  attachments,  their  contractions 
assist  these  muscles  in  drawing  down  the  ribs. 

Triangularis  Sterni. — There  has  never  been  any  doubt 
concerning  the  expiratory  function  of  the  triangularis  sterni. 
From  its  origin,  the  ensiform  cartilage,  lower  borders  of  the 
sternum,  and  lower  three  or  four  costal  cartilages,  it  acts 
upon  the  cartilages  of  the  second,  third,  fourth,  and  fifth  ribs, 
to  which  it  is  attached,  drawing  them  downwards,  and  thus 
diminishing  the  capacity  of  the  chest. 

The  above-mentioned  muscles  are  called  into  action  in 
ordinary  tranquil  respiration,  and  their  sole  function  is  to 
diminish  the  capacity  of  the  chest.  In  labored  or  difficult 
expiration,  and  in  the  acts  of  blowing,  phonation,  etc.,  other 
muscles,  which  are  called  auxiliaries,  play  a  more  or  less 
important  part.  These  muscles  all  enter  into  the  formation 
of  the  walls  of  the  abdomen,  and  their  general  action  in 
expiration  is  to  press  the  abdominal  viscera  and  diaphragm 
into  the  thorax,  and  diminish  its  vertical  diameter.  Their 
action  is  voluntary ;  and  by  an  effort  of  the  will  it  may  be 


388  RESPIKATION. 

opposed  more  or  less  by  the  diaphragm,  by  which  means  the 
duration  or  intensity  of  the  expiratory  act  is  regulated. 
They  are  also  attached  to  the  ribs  or  costal  cartilages,  and 
while  they  press  up  the  diaphragm,  depress  the  ribs,  and 
thus  diminish  the  antero-postemr  and  transverse  diameters 
of  the  chest.  In  this  action  they  may  be  opposed  by  the 
voluntary  action  of  the  muscles  which  raise  the  ribs,  also 
for  the  purpose  of  regulating  the  character  of  the  expiratory 
act.  The  importance  of  this  kind  of  action  in  declamation, 
singing,  blowing,  etc.,  is  evident;  and  the  skill  exhibited  by 
vocalists  and  performers  on  wind  instruments  shows  how 
delicately  this  may  be  regulated  by  practice. 

In  labored  respiration  in  disease,  and  in  the  hurried 
respiration  after  violent  exercise,  the  auxiliary  muscles  of  ex- 
piration, as  well  as  of  inspiration,  are  called  into  action  to  a 
considerable  extent. 

Obliquus  Externus. — This  muscle,  in  connection  with  the 
obliquus  internus  and  transversalis,  is  efficient  in  forced  or 
labored  expiration,  by  pressing  the  abdominal  viscera 
against  the  diaphragm.  Its  fibres  run  obliquely  from  above 
downwards  and  forwards.  Acting  from  its  attachments  to 
the  linea  alba,  crest  of  the  ileum,  and  Poupart's  ligament,  by 
its  attachment  to  the  eight  inferior  ribs,  it  draws  the  ribs 
downwards. 

ObliquiCs  Internus. — This  muscle  also  acts  in  forced  expi- 
ration by  compressing  the  abdominal  viscera.  The  direction 
of  its  fibres  is  from  below  upwards  and  forwards.  Acting 
from  its  attachments  to  the  crest  of  the  ileum,  Poupart's  lig- 
ament, and  the  lumbar  fascia,  by  its  attachments  to  the  carti- 
lages of  the  four  inferior  ribs,  it  draws  them  downwards. 
The  direction  of  the  fibres  of  this  muscle  is  the  same  as  that 
of  the  internal  intercostals.  By  its  action  the  ribs  are  drawn 
inwards  as  well  as  downwards. 

Transversalis. — The  expiratory  action  of  this  muscle  is 
mainly  in  compressing  the  abdominal  viscera. 


TYPES   OF   RESPIRATION.  389 

Sacro-lwnbalis. — This  muscle  is  situated  at  the  posterior 
portion  of  the  abdomen  and  thorax.  Its  fibres  pass  from  its 
origin  at  the  sacrum,  upwards  and  a  little  outwards,  to  be 
inserted  into  the  six  inferior  ribs  at  their  angles.  In  expira- 
tion it  draws  the  ribs  downwards,  acting  as  an  antagonist  to 
the  lower  levatores  costarum. 

There  are  some  other  muscles  which  may  be  brought  into 
action  in  forced  expiration,  assisting  in  the  depression  of  the 
ribs ;  such  as  the  serratus  posticus  inferior,  the  superior  fibres 
of  the  serratus  magnus,  the  inferior  portion  of  the  trapezius ; 
but  their  function  is  unimportant.1 

Types  of  Respiration. — In  the  expansive  movements  of 
the  chest,  though  all  the  muscles  which  have  been  classed  as 
ordinary  inspiratory  muscles  are  brought  into  action  to  a 
greater  or  less  extent,  the  fact  that  certain  sets  may  act  in  a 
more  marked  manner  than  others  has  led  physiologists  to 
recognize  different  types  of  respiration.  Following  Beau 
and  Maissiat,  three  types  are  generally  given  in  works  on 
physiology : 2 

1.  The  Abdominal  type. — In  this,  the  action  of  the  dia- 
phragm, and  the  consequent  movements  of  the  abdomen,  are 
most  prominent. 

2.  The' Inferior  Costal  type. — In  this,  the  action  of  the 
muscles  which  expand  the  lower  part  of  the  thorax,  from 
the  seventh  rib  inclusive,  is  most  prominent. 

3.  The  Superior  Costal  type. — In  this,  the  action  of  the 
muscles  which  dilate  the  thorax  above  the  seventh  rib,  and 
which  elevate  the  entire  chest,  is  most  prominent. 

1  It  is  uncertain  whether  the  straight  muscles  of  the  abdomen  are  ever  con- 
cerned hi  expiration.  From  their  situation,  it  might  be  supposed  that  they  would 
have  some  action  in  the  more  violent  phenomena  of  expiration,  such  as  sneezing, 
toughing,  crying,  etc. ;  but  Beau  and  Maissiat,  who  have  investigated  these  ques- 
tions very  carefully,  state  that  in  dogs  they  have  never  seen  these  muscles  act, 
even  in  the  most  violent  efforts.  (Archives  Generates^  4th  series,  vol.  iii.) 

8  Loc.  cit. 


390  RESPIRATION. 

The  abdominal  type  is  most  marked  in  children  under 
the  age  of  three  years,  irrespective  of  sex.  In  them,  respira- 
tion is  carried  on  almost  exclusively  by  the  diaphragm. 

At  a  variable  period  after  birth,  a  difference  in  the  types 
of  respiration  in  the  sexes  begins  to  show  itself.  In  the  male 
the  abdominal,  conjoined  with  th£  inferior  costal  type,  is  pre- 
dominant, and  continues  thus  through  life.  In  the  female  the 
inferior  costal  type  is  insignificant,  and  the  superior  costal 
type  predominates.  Observers  differ  in  their  statements  of 
the  period  when  this  distinction  in  the  sexes  becomes  appa- 
rent. Haller  states  that  he  observed  a  difference  in  children 
less  than  a  year  old.  Beau  and  Maissiat  state  that  after  the 
age  of  three  years  the  superior  costal  type  begins  to  be  marked 
in  the  female.  Sibson  states  that  no  great  difference  is  ob- 
servable before  the  age  of  ten  or  twelve  years.1  Without 
discussing  the  nice  question  as  to  the  exact  age  when  this 
difference  in  the  sexes  first  makes  its  appearance,  it  may  be 
stated  in  general  terms,  that  shortly  before  the  age  of  pu- 
berty, in  the  female,  the  superior  costal  type  becomes  more 
marked,  and  soon  predominates ;  while  in  the  male,  respira- 
tion continues  to  be  carried  on  mainly  by  the  diaphragm  and 
lower  part  of  the  chest. 

The  cause  of  the  excessive  movements  of  the  upper  part 
of  the  chest  in  the  female  has  been  the  subject  of  considerable 
discussion.  It  is  evident  that  it  is  not  due  to  the  mode  of 
dress  now  so  general  in  civilized  countries,  which  confines  the 
lower  part  of  the  chest,  and  would  render  movements  of  ex- 
pansion somewhat  difficult,  for  the  same  phenomenon  is  ob- 
served in  young  girls,  and  others  who  have  never  made  use 
of  such  appliances.  But  there  is  evidently  a  physiological 
condition,  the  enlargement  of  the  uterus  in  gestation,  which 
at  certain  times  would  nearly  arrest  all  respiratory  move- 
ments, excepting  those  of  the  upper  part  of  the  chest.  The 
peculiar  mode  of  respiration  in  the  female  is  a  provision  of 
Nature  against  the  mechanical  difficulties  which  would  other- 

1  LONGET,  Traite  de  Physiologie,  Paris,  1861,  tome  i.,  p.  617- 


FREQUENCY   OF  RESPIRATORY  MOVEMENTS.  391 

wise  follow  the  physiological  enlargement  of  the  uterus.  In 
pathology  it  is  observed  that,  in  consequence  of  this  peculiar- 
ity, females  are  able  to  carry,  without  great  inconvenience, 
immense  quantities  of  water  in  the  abdominal  cavity ;  while 
a  much  smaller  quantity,  in  the  male,  produces  great  distress 
from  difficulty  of  breathing.1 

Frequency  of  the  Respiratory  Movements. — In  counting 
the  respiratory  acts,  it  is  desirable  that  the  subject  be  uncon- 
scious of  the  observation,  otherwise  their  normal  character  is 
apt  to  be  disturbed.  Of  all  who  have  written  on  this  sub- 
ject, Hutchinson  presents  the  most  numerous  and  convincing 
collection  of  facts.  This  observer  ascertained  the  number  of 
respiratory  acts  per  minute,  in  the  sitting  posture,  in  1,897 
males.  The  results  of  his  observations,  with  reference  to  fre- 
quency, are  given  in  the  following  table : a 

Bespirations  per  minute.                                                                    Number  of  cases. 
From  9  to  16 79 

16     239 

17    105 

18     195 

19 74 

20     561 

21     129 

22     143 

23     42 

24     243 

24  to  40 87 

Though  this  table  shows  considerable  variation  in  differ- 
ent individuals,  the  great  majority  (1,Y31)  breathed  from  six- 
teen to  twenty-four  times  per  minute.  Nearly  a  third 
breathed  twenty  times  per  minute,  a  number  which  may  be 
taken  as  the  average. 

1  Modifications  of  the  types  of  respiration  by  disease  are  frequently  very 
marked.  In  peritonitis,  when  movements  of  the  diaphragm  would  be  productive 
of  excessive  pain,  the  abdominal  type  may  be  wholly  suppressed.  In  the  early 
stages  of  acute  pleurisy,  the  affected  side  may  become  nearly  or  quite  motionless. 

a  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iv.,  part  ii.,  p.  1085. 


392  RESPIRATION. 

The  relations  of  the  respiratory  acts  to  the  pulse  are  quite 
constant  in  health.  It  has  been  shown  by  Hutchinson  that 
the  proportion  in  the  great  majority  of  instances  is  one  re- 
spiratory act  to  every  four  pulsations  of  the  heart.  The  same 
proportion  generally  obtains  when  the  pulse  is  accelerated  in 
disease,  except  when  the  pulmonary  organs  are  involved. 

Age  has  an  influence  on  the  frequency  of  the  respiratory 
acts,  corresponding  with  what  we  have  already  noted  with 
regard  to  the  pulsations  of  the  heart. 

Quetelet  gives  the  following  as  the  results  of  observations 
on  300  males : 

44  respirations  per  minute  soon  after  birth ; 

26,  at  the  age  of  five  years  ; 

20,  at  the  age  of  fifteen  to  twenty  years ; 

19,  at  the  age  of  twenty  to  twenty-five  years ; 

16,  about  the  thirtieth  year ; 

18,  from  thirty  to  fifty  years. 

The  influence  of  sex  is  not  marked  in  very  young  chil- 
dren. The  same  observer  noted  no  difference  between  males 
and  females  at  birth ;  but  in  young  women  the  respirations 
are  a  little  less  frequent  than  in  young  men  of  the  same 


The  various  physiological  conditions  which  have  been 
noted  as  affecting  the  pulse  have  a  corresponding  influence 
on  respiration.  In  sleep  the  number  of  respiratory  acts  is 
diminished  about  twenty  per  cent  (Quetelet).  Muscular  ef- 
fort accelerates  the  respiration  pari  passu  with  the  move- 
ments of  the  heart. 

Relations  of  Inspiration  and  Expiration  to  each  other. — 
The  Respiratory  Sounds. — In  ordinary  respiration,  inspira- 
tion is  produced  by  the  action  of  muscles,  and  expiration,  in 
greatest  part,  by  the  passive  reaction  of  the  elastic  walls  of 
the  thorax  and  the  lungs.  The  inspiratory  and  expiratory 
acts  do  not  immediately  follow  each  other.  Commencing 

1  MILNE-EDWARDS,  Lemons  de  Physiologic,  tome  ii.,  pp.  482,  483. 


RELATIONS   OF  INSPIRATION  AND  EXPIRATION.  393 

with  inspiration,  it  is  found  that  this  act  maintains  about  the 
same  intensity  from  its  commencement  to  its  termination; 
there  is  then  a  very  brief  interval,  when  expiration  follows, 
which  has  its  maximum  of  intensity  at  the  commencement 
of  the  act,  and  gradually  dies  away.1  Between  the  acts  of  ex- 
piration and  inspiration  is  an  interval,  somewhat  longer  than 
that  which  occurs  after  inspiration. 

The  duration  of  expiration  is  generally  somewhat  greater 
than  that  of  inspiration,  though  they  may  be  nearly,  or  in 
some  instances  quite,  equal. 

After  from  five  to  eight  ordinary  respiratory  acts,  one 
generally  occurs  which  is  rather  more  profound  than  the  rest, 
and  by  which  the  air  in  the  lungs  is  more  effectually  changed. 
The  temporary  arrest  of  the  acts  of  respiration  in  all  violent 
muscular  efforts,  in  straining,  in  parturition,  etc.,  is  familiar 
to  all. 

Ordinarily  respiration  is  not  accompanied  by  any  sound 
which  can  be  heard  without  applying  the  ear  directly,  or  by 
the  intervention  of  a  stethoscope,  to  the  respiratory  organs ; 
excepting  when  the  mouth  is  closed,  and  breathing  is  carried 
on  exclusively  through  the  nasal  passages,  when  a  soft, 
breezy  murmur  accompanies  both  acts.  If  the  mouth  be 
sufficiently  opened  to  admit  the  free  passage  of  air,  no  sound 
is  to  be  heard  in  health.  In  sleep,  the  respirations  are  un- 
usually profound ;  and  if  the  mouth  be  closed,  the  sound  is 
rather  more  intense  than  usual. 

Snoring,  a  peculiar  sound,  more  or  less  marked,  which 
sometimes  accompanies  the  respiratory  acts  during  sleep,  oc- 
curs when  the  air  passes  through  both  the  mouth  and  the 
nose.  It  is  more  marked  in  inspiration,  sometimes  accom- 
panying both  acts,  and  sometimes  not  heard  in  expiration. 
It  is  not  necessary  to  describe  the  characters  of  a  sound  so 

1  la  listening  to  the  respiratory  murmur  over  the  substance  of  the  lungs,  the 
expiratory  follows  the  inspiratory  sound  without  an  interval  (see  p.  395).  The 
interval  between  the  acts  of  inspiration  and  expiration  is  only  appreciated  as  the 
air  passes  in  and  out  at  the  mouth. 


394:  EESPIEATION. 

familiar.  Snoring  is  an  idiosyncrasy  with  many  individuals, 
though  those  who  do  not  snore  habitually  may  do  so  when 
the  system  is  unusually  exhausted  and  relaxed.  It  only  oc- 
curs when  the  mouth  is  open,  and  the  sound  is  produced  by 
a  vibration,  and  sort  of  flapping,  of  the  velum  pendulum  pa- 
lati  between  the  two  currents  of  air  from  the  mouth  and 
nose,  together  with  a  vibration  in  the  column  of  air  itself. 

The  auscultatory  phenomena  which  accompany  the  act  of 
respiration  have  been  made  the  subject  of  special  experimen- 
tal observations  by  Dr.  Flint,  who,  from  carefully  recorded 
examinations  of  a  large  number  of  healthy  persons,  has  ar- 
rived at  the  following  conclusions : 1 

Applying  the  stethoscope  over  the  larynx  or  trachea,  a 
sound  is  heard,  of  a  distinctly  and  purely  tubular  character, 
accompanying  both  acts  of  respiration.  In  inspiration,  "  it 
attains  its  maximum  of  intensity  quickly  after  the  develop- 
ment of  the  sound,  and  maintains  the  same  intensity  to  the 
close  of  the  act,  when  the  sound  abruptly  ends,  as  if  sudden- 
ly cut  off."  After  a  brief  interval,  the  sound  of  expiration 
follows.  This  is  also  tubular  in  quality ;  it  soon  attains  its 
maximum  of  intensity,  but,  unlike  the  sound  of  inspiration, 
gradually  dies  away  and  is  lost  imperceptibly.  It  is  seen 
that  these  phenomena  correspond  with  the  nature  of  the  two 
acts  of  respiration. 

Sounds  approximating  in  character  to  the  foregoing  are 
heard  over  the  bronchial  tubes  before  they  penetrate  the 
lungs. 

Over  the  substance  of  the  lungs,  a  sound  may  be  heard 
entirely  different  in  its  character  from  that  heard  over  the 
larynx,  trachea,  or  bronchial  tubes.  In  inspiration,  the  sound 
is  much  less  intense  than  over  the  trachea,  and  has  a  breezy, 
expansive,  or  what  is  called  in  auscultation  a  vesicular  char- 
acter. It  is  much  lower  in  pitch  than  the  tracheal  sound.  It 

1  FLINT,  Physical  Exploration  and  Diagnosis  of  Diseases  affecting  the  Respi- 
ratory Organs,  Philadelphia,  1856,  p.  137  et  seq.  We  give  but  a  brief  summary 
of  these  results,  which  are  specially  applied  to  auscultation  iu  disease. 


COUGHING,   SNEEZING,    ETC.  395 

is  continuous,  and  rather  increases  in  intensity  from  its  com- 
mencement to  its  termination;  ending  abruptly,  like  the 
tracheal  inspiratory  sound.  The  sound  is  produced  in  part 
by  the  movement  of  air  in  the  small  bronchial  tubes,  but 
chiefly  by  the  expansion  of  the  innumerable  air-cells  of  the 
lungs.  It  is  followed,  without  an  interval,  by  the  sound  of 
expiration,  which  is  shorter,  one-fifth  to  one-fourth  as  long, 
lower  in  pitch,  and  very  much  less  intense.  A  sound  is  not 
always  heard  in  expiration.  In  fifteen  examinations  record- 
ed by  Dr.  Flint,  five  presented  no  expiratory  sound. 

The  variations  in  the  intensity  of  the  respiratory  sounds 
in  different  individuals  are  very  considerable.  As  a  rule 
they  are  more  intense  in  young  persons;  which  has  given 
rise  to  the  term  puerile  respiration,  when  the  sounds  are 
exaggerated  in  parts  of  the  lung,  in  certain  cases  of  disease. 
The  sounds  are  generally  more  intense  in  females  than  in 
males,  particularly  in  the  upper  regions  of  the  thorax. 

It  is  difficult  by  any  description  or  comparison  to  convey 
an  accurate  idea  of  the  character  of  the  sounds  heard  over 
the  lungs  and  air-passages ;  and  it  is  superfluous  to  make  the 
attempt,  when  they  can  be  so  easily  studied  in  the  living 
subject. 

Coughing^  /Sneezing,  Sighing,  Yawning,  Laughing,  Sobbing, 
and  Hiccough. 

These  peculiar  acts  demand  a  few  words  of  explanation. 

Coughing  and  sneezing  are  generally  involuntary  acts, 
produced  by  irritation  in  the  air-tubes  or  nasal  passages ; 
though  cough  is  often  voluntary.  In  both  of  these  acts  there 
is  first  a  deep  inspiration,  followed  by  convulsive  action  of 
the  expiratory  muscles,  by  which  the  air  is  violently  expelled 
with  a  characteristic  sound,  in  the  one  case  by  the  mouth, 
and  in  the  other  by  the  mouth  and  nares.  Foreign  bodies 
lodged  in  the  air-passages  are  frequently  expelled  in  violent 
fits  of  coughing.  In  hypersecretion  of  the  bronchial  mucous 


396  RESPIRATION. 

membrane,  the  accumulated  mucus  is  carried  by  the  act 
of  coughing  either  to  the  mouth,  or  well  into  the  larynx, 
whence  it  is  expelled  by  the  act  of  expectoration.  When 
either  of  these  acts  is  the  result  of  irritation,  either  from  a 
foreign  substance  or  secretions,  it  may  be  modified  or  partly 
smothered  by  the  will,  but  is  not  completely  under  control. 
The  exquisite  sensibility  of  the  mucous  membrane  at 
the  summit  of  the  air-passages,  under  most  circumstances, 
protects  them  from  the  entrance  of  foreign  matter,  both 
liquid  and  solid ;  for  the  slightest  impression  received  by  the 
membrane  gives  rise  to  a  violent  and  involuntary  cough,  by 
which  the  offending  matter  is  removed.  The  glottis  is  also 
spasmodically  closed. 

In  sighing,  a  prolonged  and  deep  inspiration  is  followed 
by  a  rapid  and  generally  audible  expiration.  This  occurs,  as 
a  general  rule,  once  in  every  five  to  eight  respiratory  acts, 
for  the  purpose  of  changing  the  air  in  the  lungs  more  com- 
pletely, and  is  due  to  an  exaggeration  of  the  cause  which 
gives  rise  to  the  ordinary  acts  of  respiration.  "When  due 
to  depressing  emotions,  it  has  the  same  cause ;  for  at  such 
times,  respiration  is  less  effectually  performed.  Yawning 
is  an  analogous  process,  but  differs  from  sighing  in  the 
fact  that  it  is  involuntary,  and  cannot  be  produced  by  an 
effort  of  the  will.  It  is  characterized  by  a  wide  opening  of 
the  mouth,  and  a  very  profound  inspiration.  Yawning  is 
generally  assumed  to  be  an  evidence  of  fatigue,  but  it  often 
occurs  from  a  sort  of  contagion.  When  not  the  result  of 
imitation,  it  has  the  same  exciting  cause  as  sighing,  viz.,  defi- 
cient oxygenation  of  the  blood,  and  is  followed  by  a  sense  of 
satisfaction,  which  shows  that  it  meets  some  decided  want  on 
the  part  of  the  system. 

Laughing  and  sobbing,  though  expressing  opposite  condi- 
tions, are  produced  by  very  much  the  same  mechanism. 
The  characteristic  sounds  accompanying  these  acts  are  the 
result  of  short,  rapid,  and  convulsive  movements  of  the  dia- 
phragm, accompanied  by  contractions  of  the  muscles  of  the 


CAPACITY  OF  THE  LUNGS.  397 

face,  which  produce  the  expressions  characteristic  of  hilarity 
or  grief.  Though  to  a  certain  extent  under  the  control  of 
the  will,  they  are  mostly  involuntary.  Yiolent  and  convul- 
sive laughter  may  be  excited  in  many  individuals  by  titilla- 
tion  of  certain  portions  of  the  surface  of  the  body.  Laugh- 
ter and  sometimes  sobbing,  like  yawning,  may  be  the  result 
of  involuntary  imitation. 

Hiccough  is  a  peculiar  modification  of  the  act  of  inspira- 
tion, to  which  it  is  exclusively  confined.  It  is  produced  by 
a  sudden,  convulsive,  and  entirely  involuntary  contraction  of 
the  diaphragm,  accompanied  by  a  spasmodic  constriction  of 
the  glottis.  The  contraction  of  the  diaphragm  is  more  exten- 
sive than  in  laughing  and  sobbing,  and  occurs  only  once  in 
four  or  five  respiratory  acts.  The  causes  which  give  rise  to 
hiccough  are  numerous,  and  many  of  them  are  referable  to 
the  digestive  system.  Among  these  may  be  mentioned  the 
rapid  ingestion  of  a  quantity  of  dry  food,  or  of  effervescing  or 
alcoholic  drinks.  It  occurs  frequently  in  cases  of  disease. 

Capacity  of  the  Lungs,  and  the  Quantity  of  Air  changed  in 
the  Respiratory  Acts. 

Several  points  of  considerable  physiological  interest  arise 
in  this  connection.  It  is  evident  from  the  simple  experiment 
of  opening  the  chest,  when  the  elastic  lungs  collapse  and  ex- 
pel a  certain  quantity  of  air  which  cannot  be  removed  while 
the  lungs  are  in  situ,  that  a  part  of  the  gaseous  contents  of 
these  organs  necessarily  remains  after  the  most  complete  and 
forcible  expiration.  After  an  ordinary  expiration,  there  is  a 
certain  quantity  of  air  in  the  lungs  which  can  be  expelled  by 
a  forced  expiration.  In  ordinary  respiration,  a  comparatively 
small  volume  of  air  is  introduced  with  inspiration,  which  is 
expelled  by  the  succeeding  expiration.1  By  the  extreme  action 

1  Experiments  have  shown  that  a  certain  volume  of  air  is  lost  in  the  lungs, 
the  expired  air  being  a  little  less  in  volume  than  the  quantity  inspired  (from  Vu 
to  o1^).  This  is  not  taken  into  account  in  this  connection. 


RESPIRATION. 

of  all  the  inspiratory  muscles  in  a  forced  inspiration,  a  sup- 
plemental quantity  of  air  may  be  introduced  into  the  lungs, 
which  then  contain  much  more  than  they  ever  do  in  ordi- 
nary respiration.  For  convenience,  many  physiologists  have 
adopted  the  following  names,  which  are  applied  to  these 
various  volumes  of  air : 

1.  Residual  Air  /  that  which  is  not,  and  cannot  be,  ex- 
pelled by  a  forced  expiration. 

2.  Reserve  Air ;  that  which  remains  after  an  ordinary 
expiration,  deducting  the  residual  air. 

3.  Tidal,  or  ordinary  Breathing  Air  /   that  which  is 
changed  by  the  ordinary  acts  of  inspiration  and  expiration. 

4.  Complemented  Air  /  the   excess    over  the  ordinary 
breathing  air,  which  may  be  introduced  by  a  forcible  inspi- 
ration. 

The  questions  relating  to  the  above  divisions  of  the  re- 
spired air  have  been  made  the  subject  of  numerous  investiga- 
tions ;  but  though  at  first  it  might  seem,  easy  to  determine  all 
of  them  by  a  sufficient  number  of  experiments,  the  necessary 
observations  are  attended  with  considerable  difficulty,  and  the 
sources  of  error  are  numerous.  In  measuring  the  air  changed 
in  ordinary  breathing,  it  has  been  found  that  the  acts  of  res- 
piration are  so  easily  influenced  by  the  mind,  and  it  is  so 
difficult  to  experiment  on  any  individual  without  his  knowl- 
edge, that  the  results  of  many  good  observers  are  not  to  be 
relied  upon.  This  is  one  of  the  most  important  of  the  ques- 
tions under  consideration.  The  difficulties  in  the  way  of 
estimating  with  accuracy  the  residual,  reserve,  or  comple- 
mental  volumes,  will  readily  suggest  themselves.  The  ob- 
servations on  these  points,  which  may  be  taken  as  the  most 
definite  and  exact,  are  those  of  Herbst  of  Gottingen,  and 
Hutchinson  of  England.1  Those  of  the  last-named  observer 

1  A  summary  of  the  observations  of  Herbst,  made  in  1828,  is  to  be  found  in  the 
Archives  Generates  de  Medecine,  tome  xxi.,  p.  412.     The  observations  of  Hutch- 


RESERVE  AIR.  399 

are  exceedingly  elaborate,  and  were  made  on  an  immense 
number  of  subjects  of  both  sexes,  and  of  all  ages  and  occupa- 
tions. They  are  generally  accepted  by  physiologists  as  the 
most  extended  and  accurate. 

Residual  Air. — Perhaps  there  is  not  one  of  the  questions 
under  consideration  more  difficult  to  answer  definitely  than 
that  of  the  quantity  of  air  which  remains  in  the  lungs  after  a 
forced  expiration  ;  but  fortunately  it  is  not  one  of  any  great 
practical  importance.  The  residual  air  remains  in  the  lungs 
as  a  physical  necessity.  The  lungs  are  always,  in  health,  in 
contact  with  the  walls  of  the  thorax ;  and  when  this  cavity 
is  reduced  to  its  smallest  dimensions,  it  is  impossible  that 
any  more  air  should  be  expelled.  The  volume  which  thus 
remains  has  been  variously  estimated  at  from  40  cubic  inches 
(Fontana)  to  220  cubic  inches  (Jurin).  Dr.  Hutchinson,  who 
has  carefully  considered  this  point,  estimates  the  residual 
volume  at  about  100  cubic  inches,  but  states  that  it  varies 
very  considerably  in  different  individuals.  Taking  every 
thing  into  consideration,  we  may  assume  this  estimate  to  be 
as  nearly  correct  as  any.  It  is  certain  that  the  lungs  of  a 
man  of  ordinary  size,  at  their  minimum  of  distention,  contain 
more  than  40  cubic  inches  of  air ;  and  from  measurements 
of  the  capacity  of  the  thorax,  deducting  the  estimated  space 
occupied  by  the  heart  and  vessels  and  the  parenchyma  of 
the  lungs,  it  is  shown  that  the  residual  air  cannot  amount  to 
any  thing  like  200  cubic  inches.1 

There  is  no  special  division  of  the  function  of  res- 
piration connected  with  the  residual  air.  It  remains  in 
the  lungs  merely  as  a  physical  necessity,  and  its  volume 
must  not  be  taken  into  account  in  considering  the  volumes 

inson  are  contained  in  extemo  in  the  Cyclopcedia  of  Anatomy  and  Physiology,  vol. 
iv.,  part  1,  article  Thorax. 

1  Hutchinson  found  the  mean  absolute  capacity  of  the  thorax  to  be  312  cubic 
inches.  He  allows  100  cubic  inches  for  the  heart  and  blood-vessels,  and  100  for 
the  parenchyma  of  the  lungs,  leaving  about  100  for  the  residual  volume  Op.  cit., 
p.  1067. 


400  RESPIRATION. 

which  are  changed  in  any  of  the  operations  connected  with 
breathing. 


Air.  —  This  name  is  appropriately  given  to  the 
volume  of  air  which  may  be  expelled  and  changed  by  a  vol- 
untary effort,  but  which  remains  in  the  lungs,  added  to  the 
residual  air,  after  an  ordinary  act  of  expiration.  It  may  be 
estimated,  without  any  reference  to  the  residual  air,  by  for- 
cibly expelling  air  from  the  lungs,  after  an  ordinary  expira- 
tion. The  average  volume  is  100  cubic  inches.1 

The  reserve  air  is  changed  whenever  we  experience  a 
necessity  for  a  more  complete  renovation  of  the  contents  of 
the  lungs  than  ordinary.  It  is  encroached  upon  in  the  unu- 
sually profound  inspiration  and  expiration  which  occur  every 
five  or  six  acts.  It  is  used  in  certain  prolonged  vocal  efforts, 
in  blowing,  etc. 

Added  to  the  residual  air,  it  constitutes  the  minimum 
capacity  of  the  lungs  in  ordinary  respiration.  As  it  is  con- 
tinually receiving  watery  vapor  and  carbonic  acid,  it  is  always 
more  or  less  vitiated  ;  and  when  reen  forced  by  the  breathing 
air,  which  enters  with  inspiration,  is  continually  in  circulation, 
in  obedience  to  the  law  of  the  diffusion  of  gases.  Those  who 
are  in  the  habit  of  arresting  respiration  for  a  time,  as  the 
pearl-diver,  learn  to  change  the  reserve  air  as  completely  as 
possible  by  several  forcible  acts,  and  then  fill  the  lungs  with 
fresh  air.  In  this  way  they  are  enabled  to  suspend  the  re- 
spiratory acts  for  from  one  to  two  minutes  without  inconven- 
ience. The  introduction  of  the  fresh  air  with  each  inspira- 
tion, and  the  constant  diffusion  which  is  going  on,  and  by 
which  the  proper  quantity  of  oxygen  finds  its  way  to  the  air- 
cells,  gives,  in  ordinary  breathing,  a  composition  to  the  air 
in  the  deepest  portions  of  the  lungs  which  insures  a  constant 
aeration  of  the  blood.  The  slight  difference  in  the  rapidity 
of  oxidation  between  inspiration  and  expiration  is  only  suffi- 
cient to  give  rise  to  the  involuntary  reflex  acts  of  respiration, 

1  HUTCHINSON,  IOC.  df. 


COMPLEMENTAL  AIR.  401 

and  is  not  sufficiently  marked  to  produce  any  sensation,  such 
as  is  experienced  when  respiration  is  in  the  slightest  degree 
interrupted. 

Tidal,  or  Ordinary  Breathing  Air. — The  volume  of 
air  which  is  changed  in  the  ordinary  acts  of  respiration  is 
subject  to  immense  physiological  variations,  and  the  respira- 
tory movements,  as  regards  intensity,  are  so  easily  influenced 
by  the  mind,  that  great  care  is  necessary  to  avoid  error  in 
estimating  the  volume  of  ordinary  breathing  air.  The  esti- 
mates of  Herbst  and  of  Hutchinson  are  the  results  of  very 
extended  observations  made  with  great  care,  and  are  gener- 
ally acknowledged  to  be  as  nearly  accurate  as  possible.  As 
a  mean  of  these  observations,  it  has  been  found  that  the 
average  volume  of  breathing  air,  in  a  man  of  ordinary  stat- 
ure, is  20  cubic  inches.  According  to  Hutchinson,  in  perfect 
repose,  when  the  respiratory  movements  are  hardly  percep- 
tible, not  more  than  from  7  to  12  cubic  inches  are  changed ; 
while,  under  excitement,  he  has  seen  the  volume  increased  to 
77  cubic  inches.  Of  course  the  latter  is  temporary.1  Herbst 
noted  that  the  breathing  volume  is  constantly  increased  in 
proportion  to  the  stature  of  the  individual,  and  bears  no  defi- 
nite relation  to  the  apparent  capacity  of  the  chest. 

Complemental  Air. — The  thorax  may  be  so  enlarged  by 
an  extreme  voluntary  inspiratory  effort,  as  to  contain  a  quan- 
tity of  air  much  larger  than  after  an  ordinary  inspiration. 
The  additional  volume  of  air  thus  taken  in  may  be  estimated 
by  measuring  all  the  air  which  can  be  expelled  from  the 
lungs  after  the  most  profound  inspiration,  and  deducting  the 
sum  of  the  reserve  air  and  breathing  air.  This  quantity  has 
been  found  by  Hutchinson  to  vary  in  different  individuals, 
bearing  a  close  relation  to  stature.  The  mean  complemental 
volume  is  110  cubic  inches. 

The  complemental  air  is  drawn  upon  whenever  an  effort 

1  We  have  not  thought  it  worth  while  to  enumerate  the  varied  estimates  found 
in  works  on  physiology,  which  are  not  based  on  extended  experimental  inquiry 
*  26 


402  RESPIRATION. 

is  made  which  requires  a  temporary  arrest  of  respiration. 
Brief  and  violent  muscular  exertion  is  generally  preceded  by 
a  profound  inspiration.  In  sleep,  as  the  volume  of  breathing 
air  is  somewhat  increased,  the  complemental  air  is  encroached 
upon.  A  part  or  the  whole  of  the  complemental  air  is  also 
used  in  certain  vocal  efforts,  in  blowing,  in  yawning,  in  the 
deep  inspiration  which  precedes  sneezing,  in  straining,  etc. 

Summary. — In  a  healthy  male  of  medium  stature,  the 
residual  air,  which  cannot  be  expelled  from  the  lungs, 
amounts  to  about  100  cubic  inches. 

The  reserve  air,  which  can  be  expelled,  but  which  is  not 
changed  in  ordinary  respiration,  amounts  to  about  100  cubic 
inches. 

The  tidal  air,  which  is  changed  in  ordinary  respiration, 
amounts  to  about  20  cubic  inches. 

The  complemental  air,  which  may  be  taken  into  the 
lungs  after  the  completion  of  an  ordinary  act  of  inspiration, 
amounts  to  about  110  cubic  inches.1 

1  In  Robin's  Journal  de  V Anatomic  et  de  la  Physiologie,  Sept.  1864,  p.  523 
et  seg.j  we  find  an  article  by  Dr.  Nestor  Grehant,  on  the  physical  phenomena 
of  respiration  in  man,  which  contains  some  novel  and  interesting  observations  on 
the  capacity  of  the  lungs,  volume  of  breathing  air,  etc.  The  volumes  of  air  are 
estimated  by  a  process  which  is  exceedingly  ingenious,  and  apparently  accurate ; 
but  the  number  of  observations  is  very  small  compared  with  those  of  Hutchinson, 
and  in  estimating  the  capacity  of  the  lungs,  he  does  not  take  into  consideration 
the  very  decided  influence  of  stature.  The  method  employed  is  essentially  the 
following : 

It  having  been  demonstrated  by  Regnault  and  Reiset  that  hydrogen  intro- 
duced into  the  lungs  is  not  absorbed  by  the  blood,  the  author,  taking  advantage 
of  the  well-known  property  of  gases,  by  which  they  form  a  uniform  mixture  when 
brought  hi  contact  with  each  other,  caused  the  subjects  of  his  experiments  to  re- 
spire a  measured  volume  of  hydrogen  often  enough  to  make  the  mixture  uniform, 
and  estimates,  by  analysis  of  the  expired  air,  the  quantity  which  remains  in  the 
lungs,  which  is  necessarily  represented  by  the  volume  of  hydrogen  lost.  He  as- 
certained by  experiments  that  five  respirations  of  the  gas  caused  a  perfect 
mixture. 

By  this  method  he  estimates  the  normal  capacity  of  the  lungs  after  an  ordi- 
nary expiration  (the  sum  of  the  residual  and  reserve  air),  at  from  133*65  to  191*51 
cubic  inches,  in  men  between  17  and  30  years  of  age  (p.  554). 


EXTREME  BREATHING  CAPACITY.  403 

Extreme  Breathing  Capacity. — By  the  extreme  breathing 
capacity  is  meant  the  volume  of  air  which  can  be  expelled 
from  the  lungs  by  the  most  forcible  expiration,  after  the  most 
profound  inspiration.  This  has  been  called  by  Dr.  Hutchin- 
son  the  vital  capacity r,  as  signifying  "the  volume  of  air 
which  can  be  displaced  by  living  movements."  Its  volume 
is  equal  to  the  sum  of  the  reserve  air,  the  breathing  air,  and 
the  complemental  air,  and  represents  the  extreme  capacity 
of  the  chest,  deducting  the  residual  air.  Its  physiological 
interest  is  due  to  the  fact  that  it  can  readily  .be  determined 
by  an  appropriate  apparatus,  the  spirometer,1  and  compari- 
sons can  thus  be  made  between  different  individuals,  both 
healthy  and  diseased.  The  number  of  observations  on  this 
point  made  by  Dr.  Hutchinson  is  enormous,  amounting  in 
all  to  little  short  of  five  thousand. 

The  extreme  breathing  capacity  in  health  is  subject  to 
variations  which  have  been  shown  to  bear  a  very  close  rela- 
tion to  the  stature  of  the  individual.  Hutchinson  com- 
mences with  the  proposition  that  in  a  man  of  medium  height 
(5  feet  8  inches\  it  is  equal  to  two  hundred  and  thirty  cubic 
inches.  He  has  shown  that  the  extreme  breathing  capacity 
is  constant  in  the  same  individual,  and  that  it  is  not  to  be 
increased  by  habit  or  practice. 

The  most  striking  result  of  the  experiments  of  Dr. 
Hutchinson,  with  regard  to  the  modifications  of  the  vital  ca- 

The  tidal  or  breathing  air,  he  estimates  at  30  cubic  inches. 

The  observations  of  Dr.  Grehant  are  as  yet  so  few  in  number  that  we  prefer 
to  adhere  to  the  results  of  the  greatly  extended  observations  of  Hutchinson ; 
though  the  new  method  is  very  ingenious,  and  further  experiments  will  probably 
lead  to  important  results. 

1  The  spirometer  consists  of  a  vessel  containing  water,  out  of  which  a  receiver 
is  raised  by  breathing  into  it  through  a  tube ;  the  height  to  which  the  receiver  is 
raised  indicating  the  volume  of  the  vital  capacity  (Cyclop,  of  Anat.  and  Phys., 
vol.  iv.,  part  2,  p.  1068).  In  all  the  observations  of  Dr.  Hutchinson,  he  has  taken 
care  to  see  that  the  level  of  the  water  was  the  same  in  the  receiver  and  the  reser- 
voir, and  to  carefully  correct  the  volumes  of  air  for  temperature.  All  observa- 
tions were  made  with  the  subject  erect,  and  every  thing  carefully  avoided  which 
could  interfere  with  the  free  action  of  the  respiratory  muscles. 


404 


RESPIRATION. 


pacity,  is  that  it  bears  a  definite  relation  to  stature,  without 
being  affected  in  a  very  marked  degree  by  weight,  or  the 
circumference  of  the  chest.  This  is  especially  remarkable,  as 
it  is  well  known  that  height  does  not  depend  so  much  upon 
the  length  of  the  body,  as  the  length  of  the  lower  extremities. 

It  has  been  ascertained  that  for  every  inch  in  height,  'be- 
tween five  and  six  feet,  the  extreme  breathing  capacity  is  in- 
creased eight  cubic  inches. 

The  following  table  shows  the  mean  results  of  the  im- 
mense number  of  observations  on  which  this  conclusion  is 
based : l 


Progression  of  the  Vital  Capacity  Volume  with  the  Stature. 


si 

Joo  en 

1§ 

g*  o  2 

o  2 

**"*  •*-*   « 

Height. 

s|« 

5|| 

|H 

§ 

o 

^fi 

6  feet    0  inches  )  K  ?    ,    ,  .    , 
r            o      "       V                  inch. 

1st  result 

175-0 

3d  result. 

176-0 

174-0 

5           4             [5    "      3     " 

188-5 

191-0 

190-0 

5         4           [K   «     K    « 

5           6             f5 

206-0 

207-0 

206-0 

S              fi                 ) 

5      s       k-:.-».i" 

222-0 

228-0 

222-0 

50                             i 

L  K     M       Q      " 
5          10      "       f. 

237-5 

241-0 

238-0 

5       10    "     Is  «  11    « 

6             0      "       j"5 

254-5 

258-0 

254-0 

Mean  of  all  Heights.  .  .  . 

214-0 

217-0 

214-0 

Age  has  an  influence,  though  less  marked  than  stature, 
upon  the  extreme  breathing  capacity.    As  the  result  of  4,800 

1  Op.  cit.,  p.  1072.  The  increase  in  breathing  capacity,  pari  passu  witn  an 
increase  in  height,  was  mentioned  by  Herbst  (loc.  cit.\  but  Hutchinson  was  the 
first  to  make  any  extended  observations,  and  give  any  definite  information  on 
this  point. 


EXTREME   BREATHING   CAPACITY.  405 

observations  (males),  it  was  ascertained  that  the  volume  in- 
creases with  age  up  to  the  thirtieth  year,  and  progressively 
decreases,  with  tolerable  regularity,  from  the  thirtieth  to  the 
sixtieth  year. 

These  figures,  though  necessarily  subject  to  certain  indi- 
vidual variations,  may  be  taken  as  the  basis  for  examinations 
of  the  extreme  breathing  capacity  in  disease,  which  frequently 
give  important  information.  Of  course,  the  breathing  capa- 
city is  modified  by  any  abnormal  condition  which  interferes 
with  the  mobility  of  the  thorax,  or  the  dilatability  of  the 
lungs.  Of  all  diseased  conditions,  phthisis  pulmonalis  is  the 
most  interesting  in  this  connection.  With  regard  to  the 
significance  of  the  variations  in  this  disease,  Dr.  Hutchinson 
has  arrived  at  the  following  conclusions  : 

"  It  has  been  found  that  ten  cubic  inches  below  the  due 
quantity,  i.  e.,  220  instead  of  230'  inches,  need  not  excite 
alarm ;  but  there  is  a  point  of  deficiency  in  the  breathing 
volume  at  which  it  is  difficult  to  say  whether  it  is  merely 
one  of  those  physiological  differences  dependent  on  a  certain 
irregularity  in  all  such  observations,  or  deficiency  indicative 
of  disease.  A  deficiency  of  16  per  cent,  is  suspicious.  A 
man  below  55  years  of  age  breathing  193  cubic  inches  instead 
of  230  cubic  inches,  unless  he  is  excessively  fat,  is  probably 
the  subject  of  disease. 

"  In  phthisis  pulmonalis  the  deficiency  may  amount  to 
90  per  cent.,  and  yet  life  be  maintained.  The  vital  capacity 
volume  is  likewise  a  measure  of  improvement.  A  phthisical 
patient  may  improve  so  as  to  gain  40  upon  220  cubic  inches." 

Herbst  has  shown  l  that  the  extreme  breathing  capacity 
is  diminished  by  obesity ;  that  it  is  proportionally  less  in 
females  than  in  males,  and  in  children  than  in  adults. 

Relations  in  Volume  of  the  Expired  to  the  Inspired  Air. 
— A  certain  proportion  of  the  inspired  air  is  lost  in  respira- 
tion, so  that  the  air  expired  is  always  a  little  less  in  volume 


406  RESPIRATION. 

than  that  which  is  taken  into  the  lungs.  All  the  older  ex- 
perimenters, except  Magendie,  were  agreed  upon  this  point. 
The  loss  was  put  by  Davy  at  -fa,  and  by  Cuvier  at  -^  of  the 
amount  of  air  introduced.1  Observations  on  this  point,  to  be 
exact,  must  include  a  considerable  number  of  respiratory 
acts ;  and  from  the  difficulty  of  continuing  respiration  in  a 
perfectly  regular  and  normal  manner,  when  the  attention  is  di- 
rected to  that  function,  the  most  accurate  results  may  prob- 
ably be  obtained  from  experiments  on  animals.  Despretz  a 
caused  six  young  rabbits  to  respire  for  two  hours  in  a  con- 
fined space  containing  299  cubic  inches  of  air,  and  ascertained 
that  the  volume  had  diminished  61  cubic  inches,  or  a  little 
more  than  one-fiftieth.  "We  may  take  the  approximations  of 
Davy  and  Cuvier,  as  applied  to  the  human  subject,  as  nearly 
correct,  and  assume  that  in  the  lungs,  from  -fa  to  -^  of  the 
inspired  air  is  lost. 

Diffusion  of  Air  in  the  Lungs. — When  it  is  considered 
that  with  each  inspiration  but  about  twenty  cubic  inches  of 
fresh  air  is  introduced,  sufficient  only  to  fill  the  trachea  and 
larger  bronchial  tubes,  it  is  evident  that  some  forces  must  act 
by  which  this  fresh  air  finds  its  way  into  the  air-cells,  and  the 
vitiated  air  is  brought  into  the  larger  tubes,  to  be  expelled 
with  the  succeeding  expiration.  The  expired  air  may  be- 
come so  charged  with  noxious  gases,  by  holding  the  breath 
for  a  few  seconds,  that  when  collected  in  a  receiver  under 
water,  it  is  incapable  of  supporting  combustion. 

The  interchange  between  the  fresh  air  in  the  upper  portions 
of  the  respiratory  apparatus  and  the  air  in  the  deeper  parts 
of  the  lungs  is  constantly  going  on,  in  obedience  to  the  well- 
known  law  of  the  diffusion  of  gases,  aided  by  the  active  cur- 
rents or  impulses  produced  by  the  alternate  movements  of 
the  chest.  When  two  gases,  or  mixtures  of  gases,  of  different 
densities  are  brought  in  contact  with  each  other,  they  diffuse 

1  BERABD,  Cours  de  Physiologic,  Paris,  1851,  tome  iii.,  p.  338, 
3  Idem. 


DIFFUSION   OF   AEB  IN  THE  LUNGS.  407 

or  mingle  with  great  rapidity,  until,  if  undisturbed,  the  whole 
mass  has  a  uniform  density  and  composition.  This  has  been 
shown  to  take  place  between  very  light  and  very  heavy  gases 
in  opposition  to  the  laws  of  gravity,  and  even  when  two  res- 
ervoirs are  connected  by  a  small  tube  many  feet  in  length, 
though  then  it  proceeds  quite  slowly.  In  the  respiratory  ap- 
paratus, at  the  termination  of  inspiration,  the  atmospheric 
air,  composed  of  a  mixture  of  oxygen  and  nitrogen,  is  intro- 
duced into  the  tubes  with  a  considerable  impetus,  and  is 
brought  into  contact  with  the  gas  in  the  lungs,  which  is 
much  heavier,  as  it  contains  a  considerable  quantity  of  car- 
bonic acid.  Diffusion  then  takes  place,  aided  by  the  elastic 
lungs,  which  are  gradually  forcing  the  gaseous  contents  out 
of  the  cells,  until  a  certain  portion  of  the  air  loaded  with 
carbonic  acid  finds  its  way  to  the  larger  tubes,  to  be  thrown 
off  in  expiration,  its  place  being  supplied  by  the  fresh  air. 

In  obedience  to  the  law  established  by  Graham,  that  the 
diffusibility  of  gases  is  inversely  proportionate  to  the  square 
root  of  their  densities,  the  penetration  of  atmospheric  air, 
which  is  the  lighter  gas,  to  the  deep  portions  of  the  lungs 
would  take  place  with  greater  rapidity  than  the  ascent  of  the 
air  charged  with  carbonic  acid  ;  so  that  81  parts  of  carbonic 
acid  should  be  replaced  by  95  of  oxygen.1  It  is  found,  in- 
deed, that  the  volume  of  carbonic  acid  exhaled  is  always  less 
than  the  volume  of  oxygen  absorbed. 

This  diffusion  is  constantly  going  on,  so  that  the  air  in 
the  pulmonary  vesicles,  where  the  interchange  of  gases  with 
the  blood  takes  place,  maintains  a  pretty  uniform  composi- 
tion. The  process  of  aeration  of  the  blood,  therefore,  has 
none  of  that  intermittent  character  which  attends  the  me- 
chanical processes  of  respiration,  which  would  undoubtedly 
occur  if  the  entire  gaseous  contents  of  the  lungs  were  changed 
with  every  act. 

There  is  no  evidence  sufficiently  definite  to  show  that  the 
muscular  fibres  in  the  bronchial  tubes,  which  are  of  the  un- 

3  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iv.,  part  1,  p.  362, 


408  RESPIRATION. 

striped  variety,  and  slow  and  gradual  in  their  contraction, 
have  any  thing  to  do  with  the  diffusion  of  gases  in  the  lungs ; 
nor  is  it  probable  that  any  marked  influence  is  exerted  by 
the  movements  of  the  cilioe  which  cover  the  mucous  mem- 
brane. 


CHAPTEK  XII. 

CHANGES   WHICH  THE  AIR  UNDERGOES   IN  RESPIRATION. 

General  considerations — Discovery  of  carbonic  acid — Discovery  of  oxygen — Com- 
position of  the  air — Consumption  of  oxygen — Influence  of  temperature — In- 
fluence of  sleep — Influence  of  an  increased  proportion  of  oxygen  in  the  atmos- 
phere— Temperature  of  the  expired  air — Exhalation  of  carbonic  acid — Influence 
of  age — Influence  of  sex — Influence  of  digestion — Influence  of  diet — Influence 
of  sleep — Influence  of  muscular  activity — Influence  of  moisture  and  tem- 
perature— Influence  of  seasons — Relations  between  the  quantity  of  oxygeii 
consumed  and  the  quantity  of  carbonic  acid  exhaled — Exhalation  of  watery 
vapor — Exhalation  of  ammonia — Exhalation  of  organic  matter — Exhalation 
of  nitrogen. 

FROM  the  allusions  which  have  already  been  made  to  the 
general  process  of  respiration,  it  is  apparent,  that  before  the 
discovery  of  the  nature  of  the  gases  which  compose  the  air 
and  those  which  are  exhaled  from  the  lungs,  it  was  impossible 
for  physiologists  to  have  any  correct  ideas  of  the  nature  of 
this  important  function.  It  is  not  surprising  that  the  ancients, 
observing  the  regular  introduction  of  air  into  the  lungs,  and 
noting  the  fact  that  the  air  is  generally  much  cooler  than  the 
body,  supposed  the  great  object  of  respiration  to  be  the  cool- 
ing of  the  blood.  It  is  also  evident  that  no  definite  knowl- 
edge of  any  of  the  processes  of  respiration  could  exist  prior 
to  the  discovery  of  the  circulation  of  the  blood. 

Though  it  is  foreign  to  our  purpose  to  treat  historically 
of  the  theories  concerning  any  of  the  functions  of  the  body, 
the  facts  relating  to  changes  in  the  respired  air,  which  from 


410  KESPEBATION. 

time  to  time  have  been  developed,  bear  so  close  a  relation  to 
discoveries  of  the  properties  of  certain  gases,  particularly 
carbonic  acid  and  oxygen,  that  it  seems  desirable  to  give  at 
least  a  rapid  sketch  of  these  discoveries,  and  follow  the  ad- 
vances in  our  knowledge  of  thg  processes  of  respiration,  with 
which  they  are  necessarily  connected.1 

In  the  latter  part  of  the  fifteenth  century,  Leonardo  da 
Yinci,  the  great  painter,  mathematician,  and  naturalist,  made 
a  discovery  which  conclusively  proved  the  fallacy  of  the  idea 
that  the  air  simply  cooled  the  blood  in  respiration.  He  dis- 
covered that  fire  consumed  the  air,  and  that  animals  could 
not  live  in  a  medium  which  was  incapable  of  supporting 
combustion.  This  is  the  first  statement  in  the  history  of 
science  which  points  to  the  fact  that  the  function  of  the  air 
in  respiration  depends  on  its  composition,  and  not  on  its 
physical  properties. 

About  the  middle  of  the  seventeenth  century,  Yan  Hel- 
mont  discovered  some  of  the  properties  of  what  is  now  known 
as  carbonic  acid  gas.  He  showed  that  a  gas,  the  result  of 
fermentation,  or  of  the  combustion  of  carbon,  and  formed  by 
the  action  of  vinegar  on  certain  carbonates,  was  incapable  of 
supporting  combustion  or  maintaining  animal  life.  He  rec- 
ognized this  as  the  gas  which  is  found  in  the  lower  part  of 
the  celebrated  Grotto  del  Cane,  near  Naples,  into  which  a  man 
may  enter  with  impunity,  but  which  will  asphyxiate  a  small 
animal,  as  it  is  brought  under  the  influence  of  the  lower  strata. 

A  few  years  later  (1670),  Boyle,  the  founder  of  the  Royal 
Society  of  London,  by  some  experiments  published  in  the 
Philosophical  Transactions,  attempted  to  show  that  air  was 
necessary  to  the  life  of  all  animals,  even  those  which  live 
under  water.  In  a  remarkable  paper  entitled  /Suspicions 
about  some  Hidden  Qualities  of  the  Air,  he  pointed  to  the 

1  The  reader  is  referred  to  the  elaborate  "work  of  MILNE-EDWARDS  (Legons  sur 
la  Physiologic,  tome  i.,  p.  375  et  seq.)  for  a  complete  and  highly  interesting  history 
of  the  physiology  of  respiration,  from  which  we  have  taken  most  of  the  historical 
facts  to  which  reference  will  be  made. 


CHANGES   IN  THE   AIR  IN  RESPIRATION.  411 

probable  existence  of  some  unknown  vital  substance  in  the 
atmosphere.  A  few  years  later  it  was  demonstrated  by  Ber- 
noulli, that  the  existence  of  aquatic  animals  depends  upon 
air  held  in  solution  in  the  water.  About  this  time  Robert 
Hooke  performed  his  celebrated  experiment  of  exposing  the 
lungs  of  a  living  animal,  and  maintaining  the  vital  processes 
by  artificial  respiration.  He  demonstrated  that  asphyxia 
occurred  when  he  ceased  to  change  the  air  in  the  lungs, 
though  these  organs  were  allowed  to  remain  distended. 

Fracassati  also  showed  that  the  red  color  of  the  upper 
surface  of  a  clot  of  blood  was  due  to  its  exposure  to  the  air ; 
and  Lower,  examining  the  blood  before  and  after  its  passage 
through  the  lungs,  in  artificial  respiration,  showed  that  the 
red  color  of  arterial  blood  depends  on  the  renewal  of  the 
atmosphere. 

In  1667,  Mayow  published  his  work  on  Eespiration,  in 
which  he  advanced  the  view  that  the  air  contained  a  princi- 
ple, capable  of  supporting  combustion,  which  is  absorbed  in 
respiration,  changes  venous  into  arterial  blood,  and  is  the 
cause  of  the  heat  which  is  developed  in  animal  bodies.1  The 
importance  of  this  discovery  was  not  appreciated  by  the  phys- 
iologists of  that  day ;  and  it  was  more  than  a  century  before 
it  received  its  appropriate  place  in  science. 

In  1757,  Joseph  Black,  of  Glasgow,  isolated  and  studied 
carbonic  acid,  which  he  called  fixed  air.  He  recognized  this 
gas  in  the  expired  air,  by  passing  the  breath  through  lime- 

1  We  find  the  following  passage  in  an  analysis  of  the  work  of  MAYOW  on  Res 
piration,  published  in  the  Philosophical  Transactions,  1668,  p.  833 : 

"  The  author  *  *  *  delivers  his  thoughts  on  the  use  of  Respiration,  waving 
those  opinions,  that  would  have  respiration  either  to  cool  the  heart,  or  make  the 
Bloud  pass  through  the  Lungs  out  of  the  right  ventricle  of  the  heart  to  the  left, 
or  to  reduce  the  thicker  venal  blood  into  thinner  and  finer  parts ;  and  affirming, 
That  there  is  something  in  the  Air,  absolutely  necessary  to  life,  which  is  conveyed 
into  the  Bloud;  which,  whatever  it  be,  being  exhausted,  the  rest  of  the  air  is 
made  useless,  and  no  more  fit  for  Respiration.  Where  yet  he  doth  not  exclude 
this  use,  That  with  the  expelled  Air,  the  vapors  also,  steaming  out  of  the  Bloud, 
are  thrown  out  together." 


412  RESPIRATION. 

water.  It  is  evident  that  this  was  the  gas  which  was  ob- 
served so  many  years  before  by  Yan  Helmont. 

In  1775,  Priestley  discovered  that  the  air  is  composed  of 
oxygen  and  nitrogen,  though  he  did  not  make  use  of  these 
names;  and  a  few  years  latei^  showed  that  air  which  has 
been  vitiated  by  the  respiration  of  animals  is  consumed  by 
vegetables,  which  return  the  elements  necessary  to  the  life  of 
animals.  In  a  paper  published  in  the  Philosophical  Transac- 
tions for  1776,  he  proved  that  the  change  in  the  color  of  the 
blood  in  the  lungs  is  due  to  the  absorption  of  the  newly 
discovered  oxygen ;  and  showed,  furthermore,  that  the  inter- 
change of  gases  between  the  air  and  the  blood  can  take  place 
through  membranes,  as  readily  as  when  the  two  fluids  are 
brought  directly  in  contact  with  each  other.1 

The  discoveries  above  enumerated,  though  all  bearing  on 
the  great  question,  were  simply  isolated  facts,  and  failed  to 
develop  any  definite  idea  of  the  changes  of  the  air  and  blood 
in  respiration.  The  application  of  these  facts  was  made  by 
the  great  chemist  Lavoisier ;  who  was  the  first  to  employ  the 
delicate  balance  in  chemical  investigation,  and  whose  obser- 
vations mark  the  beginning  of  an  accurate  knowledge  of  the 
function  of  respiration.  With  the  balance,  Lavoisier  showed 
the  nature  of  the  oxides  of  the  metals ;  he  discovered  that 
carbonic  acid  is  formed  by  a  union  of  carbon  and  oxygen ; 
and,  noting  the  consumption  of  oxygen  and  the  production 
of  carbonic  acid  in  respiration,  advanced,  for  the  first  time, 
the  view  that  the  one  was  employed  in  the  production  of  the 

1  BERARD  attributes  the  discovery  of  oxygen  to  Bayen  (op.  cit.,  tome  iii.,  p. 
328).  It  is  true  that  Bayen  in  1774  evolved  oxygen  by  heating  the  red  oxide  of 
mercury,  but  he  simply  saw  a  gas  given  off,  the  nature  and  properties  of  which  he 
did  not  describe.  Priestley  first  published  his  discovery  of  oxygen,  with  a  descrip- 
tion of  certain  of  its  important  properties,  in  the  same  year;  and  because  he  thus 
described  properties  which  distinguish  this  from  every  other  gas,  to  Priestley  is 
generally,  and  justly,  ascribed  the  honor  of  its  discovery.  Scheele,  in  Sweden, 
obtained  and  described  oxygen  ("  the  air  of  fire  ")  shortly  after  it  had  been  ob- 
tained by  Priestley,  without  the  knowledge  that  his  discovery  had  been  anticipated. 
His  work  was  published  in  1777. 


COMPOSITION  OF  THE  ADJ.  413 

other.  Though,  as  should  naturally  be  expected,  the  doc- 
trines of  this  great  observer  have  been  modified  with  the 
advances  in  science,  he  developed  facts  which  will  stand  for- 
ever, and  which  have  served  as  the  starting  point  of  all 
our  knowledge  on  this  subject.  From  that  time  physiol- 
ogists began  to  look  on  respiration  as  consisting  in  the  appro- 
priation of  oxygen  and  the  exhalation  of  carbonic  acid; 
and  now  the  seat  of  this  process  is  only  changed  from  the 
lungs  to  the  tissues.  From  the  limited  knowledge  of  the 
intimate  phenomena  of  nutrition  which  obtained  in  his  day, 
Lavoisier  could  not  be  expected  to  entertain  any  other  view 
than  that  the  carbonic  acid  produced  was  the  result  of  the 
direct  union  of  oxygen  with  carbon  in  the  blood.  It  is  only 
since  investigations  have  made  manifest  the  great  complexity 
of  the  processes  of  nutrition,  that  some  are  unwilling  to  be- 
lieve that  carbonic  acid  is  produced  in  as  simple  a  way  as 
it  appeared  to  Lavoisier.1 

Composition  of  the  Air. — Pure  atmospheric  air  is  a 
mechanical  mixture  of  79*19  parts  of  nitrogen  with  20'81 
parts  of  oxygen  (Dumas  and  Boussingault).2  It  contains  in 
addition  a  very  small  quantity  of  carbonic  acid,  about  one 
part  in  2,000  by  volume,  and  traces  of  ammonia.  The  air 
is  never  free  from  moisture,  which  is  very  variable  in  quan- 
tity, being  generally  more  abundant  at  a  high  than  at  a  low 
temperature.  In  1840,  Schonbein  discovered  in  the  air  a  pecu- 
liar odorous  principle  called  ozone,  which  he  conceived  to  be  a 
compound  of  oxygen  and  hydrogen  (HO3),  but  which  is  now 
pretty  well  shown  to  be  an  allotropic  form  of  oxygen.  The 

1  The  applications  of  the  discoveries  of  Lavoisier  to  the  production  of  animal 
heat  will  be  taken  up  in  connection  with  that  phenomenon. 

a  Some  chemists  suppose  that  the  oxygen  and  nitrogen  in  the  air  are  in  a  con- 
dition of  feeble  chemical  combination.  However  that  may  be,  it  is  certain  that 
in  respiration  it  is  the  oxygen  which  is  absorbed  by  the  blood,  and  which  carries 
on  the  function.  The  nitrogen  seems  to  act  simply  as  a  diluent,  thus  providing 
that  the  blood  in  the  lungs  shall  be  exposed  to  but  a  certain  quantity  of  the  re- 
spiratory principle. 


4:14:  RESPIRATION. 

oxygen  which  is  obtained  by  decomposing  water  by  the  Yol- 
taic  pile  is  in  this  condition.  It  exists  in  very  small  quantity 
in  the  air,  and  plays  no  part  in  the  function  of  respiration. 
Its  chief  interest  has  been  in  a  theoretical  connection  with 
epidemic  diseases.1  Floating  ii  the  atmosphere  are  a  num- 
ber of  excessively  minute  organic  bodies.  Yarious  odor- 
ous and  other  gaseous  matter  may  be  present  as  accidental 
constituents. 

In  considering  the  function  of  respiration,  it  is  not  neces- 
sary to  take  account  of  any  of  the  constituents  of  the  atmos- 
phere, except  oxygen  and  nitrogen ;  the  others  being  either 
inconstant,  or  existing  in  excessively  minute  quantity.  It 
is  necessary  to  the  regular  performance  of  the  function  that 
the  air  should  contain  about  four  parts  of  nitrogen  to  one  of 
oxygen,  and  have  about  the  density  which  exists  on  the  gen- 
eral surface  of  the  globe.  When  the  density  is  very  much 
increased,  as  in  mines,  respiration  is  somewhat,  though  not 
gravely,  disturbed.  By  exposure  to  a  rarefied  atmosphere,  as 
in  the  ascent  of  high  mountains  or  in  aerial  voyages,  respira- 
tion may  be  very  seriously  interfered  with,  from  the  fact  that 
less  oxygen  than  usual  is  presented  to  the  respiratory  surface, 
and  the  reduced  atmospheric  pressure  diminishes  the  capa- 
city of  the  blood  for  holding  gases  in  solution. 

Magendie  and  Bernard,  in  experimenting  on  the  minimum 
proportion  of  oxygen  in  the  air  which  is  capable  of  sustaining 
life,  found  that  a  rabbit,  confined  under  a  bell-glass  with  an 
arrangement  for  removing  the  carbonic  acid  and  water  ex- 

1  Ozone  may  be  formed  bypassing  electric  discharges  through  the  ordinary  at- 
mosphere, or  through  oxygen.  Its  proportion  in  the  air  is  supposed  to  be  much 
increased  in  storms  which  are  accompanied  by  electric  phenomena.  Schonbein 
exposed  animals  to  the  action  of  this  substance.  A  dog,  confined  for  an  hour  in 
a  bell-glass,  into  which  ozone  was  passed,  died,  though  it  was  estimated  that  he 
absorbed  only  about  *03  of  a  grain.  An  examination  showed  the  lungs  in  a  con- 
dition of  acute  inflammation.  M.  de  la  Kive,  who  has  also  experimented  upon 
it,  compares  its  action  on  the  respiratory  organs  to  that  of  chlorine  (BERNARD, 
JLefOns  sur  les  Effete  des  /Substances  Toxiques  et  Medicamenteuses,  Paris,  1857,  p. 
150). 


COMPOSITION   OF  THE  AIR.  415 

haled,  as  fast  as  they  were  produced,  died  of  asphyxia  when 
the  quantity  of  oxygen  became  reduced  to  from  3  to  5  per 
cent.1 

Following  Lavoisier,  the  Abbe  Spallanzani,2  by  researches 
on  a  great  number  of  animals  of  all  classes,  demonstrated  the 
universal  necessity  of  air,  either  in  a  gaseous  condition  or  in 
solution  in  liquids,  throughout  the  animal  kingdom. 

A  few  experiments  are  on  record  in  which  the  human 
subject  and  animals  have  been  made  to  respire  for  a  time 
pure  oxygen.  Though  this  is  the  gas  which  is  essential  in 
ordinary  respiration,  the  process  being  carried  on  about  as 
well  in  a  mixture  of  oxygen  with  hydrogen  as  with  nitrogen, 
the  functions  do  not  seem  to  be  much  altered  when  the  pure 
gas  is  taken  into  the  lungs.  Some  authors  state  that  its  pro- 
longed inhalation  exaggerates  the  function  for  a  time,  and 
that  inflammation  of  the  lungs  and  death  follow  its  pro- 
longed use ;  while  the  experiments  of  others  show  that  it  is 
harmless.  Allen  and  Pepys  confined  animals  for  twenty- 
four  hours  in  an  atmosphere  of  pure  oxygen,  without  any 
notable  results ; 3  but,  as  is  justly  remarked  by  Longet,  these 
experiments  do  not  show  that  it  would  be  possible  to  respire 
unmixed  oxygen  indefinitely  without  inconvenience.  As  it 
exists  in  the  air,  oxygen  is  undoubtedly  in  the  best  form  for 
the  permanent  maintenance  of  the  respiratory  function. 
The  blood  seems  to  have  a  certain  capacity  for  the  absorp- 
tion of  oxygen,  which  is  not  increased  when  the  pure  gas  is 
presented. 

The  only  other  gas  which  has  the  power  of  maintaining 
respiration,  even  for  a  time,  is  nitrous  oxide.  This  is  ab- 
sorbed by  the  blood-corpuscles  with  great  avidity,  and  for  a 
time  produces  an  exaggeration  of  the  vital  processes,  with 
delirium,  etc. — properties  which  have  given  it  the  common 

1  BERNARD,  op.  cit.,  p.  115. 

a  SPALLANZANI,  Memoires  sur  la  Respiration,  traduits  en  Fran$ais  cFapres  son 
manuscrit  in'edit,  1803. 

*  LONGET,  Traite  de  Physiologic,  Paris,  1861,  tome  i.,  p.  458. 


416  RESPIRATION. 

name  of  the  "  laughing  gas  " ;  but  this  condition  is  followed 
by  anaesthesia,  and  finally  asphyxia,  probably  because  the 
gas  has  such  an  affinity  for  the  blood-corpuscles  as  to  re- 
main to  a  certain  extent  fixed,  interfering  with  the  inter- 
change of  gases  which  is  essential  to  life.  Notwithstanding 
this,  experimenters  have  confined  rabbits  and  other  animals 
in  an  atmosphere  of  nitrous  oxide  for  a  number  of  hours. 
In  all  cases  they  became  asphyxiated,  but  in  some  instances 
were  restored  on  being  brought  again  into  the  atmosphere.1 

Other  gases  which  may  be  introduced  into  the  lungs 
either  produce  asphyxia,  negatively,  from  the  fact  that  they 
are  not  absorbed  by  the  blood  and  are  incapable  of  carrying 
on  respiration,  like  hydrogen  or  nitrogen,  or  positively,  by  a 
poisonous  effect  on  the  system.  The  most  important  of  the 
gases  which  act  as  poisons  are,  carbonic  oxide,  sulphuretted 
hydrogen,  and  arseniuretted  hydrogen.  It  is  somewhat  un- 
certain whether  carbonic  acid  exerts  its  deleterious  influence 
as  a  poison,  or  as  merely  taking  the  place  of  the  oxygen  in 
the  blood-corpuscles.  It  is  easily  displaced  from  the  blood 
by  oxygen,  and  therefore  does  not  seem  to  possess  the  prop- 
erties of  a  poison,  like  carbonic  oxide,  and  some  other  gases, 
which  become  fixed  in  the  blood,  and  are  not  readily  dis- 
placed when  fresh  air  is  introduced  into  the  lungs. 

Consumption  of  Oxygen. — The  determination  of  the 
quantity  of  oxygen  which  is  removed  from  the  air  by  the 
process  of  respiration  is  a  question  of  great  physiological  in- 
terest, and  one  which  engaged  largely  the  attention  of  La- 
voisier and  those  who  have  followed  in  his  line  of  observa- 
tion. On  this  point  there  is  an  accumulated  mass  of 
observations  which  are  comparatively  unimportant,  from  the 
fact  that  they  were  made  before  the  means  of  analysis  of  the 
gases  were  as  perfect  as  they  now  are.  Though  many  of  the 
results  obtained  by  the  older  experimenters  are  interesting 
and  instructive,  as  showing  the  comparative  quantities  of 

1  LONGET,  op.  dt.,  tome  i.,  p.  460. 


CONSUMPTION   OF   OXYGEN.  417 

i 

oxygen  consumed  under  various  physiological  conditions,  they 
are  not  to  be  compared  with  the  more  recent  observations, 
particularly  those  of  Kegnault  and  Eeiset,  Valentin  and  Brun- 
ner,  Dumas,  Andral  and  Gavarret,  Scharling,  and  Edward 
Smith,  with  regard  to  the  absolute  quantity  of  oxygen  made 
use  of  in  respiration.  In  the  observations  of  Regnault  and 
Reiset,  the  animal  to  be  experimented  upon  was  enclosed  in 
a  receiver  filled  with  air,  a  measured  quantity  of  oxygen 
was  introduced  as  fast  as  it  was  consumed  by  respiration,  and 
the  carbonic  acid  was  constantly  removed  and  carefully  esti- 
mated. In  most  of  the  experiments,  the  confinement  did  not 
appear  to  interfere  with  the  functions  of  the  animal,  which 
ate  and  drank  in  the  apparatus,  and  was  in  as  good  condition 
at  the  termination  as  at  the  beginning  of  the  observation. 
This  method  is  infinitely  more  accurate  than  that  of  simply 
causing  an  animal  to  breathe  in  a  confined  space,  when  the 
consumption  of  oxygen  and  accumulation  of  carbonic  acid 
and  other  matters  must  interfere  more  or  less  with  the  proper 
performance  of  the  respiratory  function.  This  is  known  as 
the  direct  method  of  investigating  the  changes  in  the  air  pro- 
duced by  respiration.  As  employed  by  Regnault  and  Reiset, 
it  is  only  adapted  to  experiments  on  animals  of  small  size. 
These  give  but  an  approximative  idea  of  the  processes  as  they 
take  place  in  the  human  subject,  as  it  is  natural  to  suppose 
that  the  relative  quantities  of  gases  consumed  and  produced 
in  respiration  vary  in  different  orders  of  animals-.1 

1  In  Robin's  Journal  de  TAnatomie  et  de  la  Physiologic,  July,  1864,  tome  i., 
p.  429,  we  find  an  analysis  of  researches  on  respiration  by  Dr.  Max  Pettenkofer,  in 
which  the  conditions  for  accurate  observations  on  the  human  subject  seem  to  be 
fulfilled.  Dr.  Pettenkofer  has  constructed  a  chamber  large  enough  to  admit  amant 
and  allow  perfect  freedom  of  motion,  eating,  sleeping,  etc.,  into  which  air  is  con- 
stantly introduced  in  definite  quantity,  and  from  which  the  products  of  respiration 
are  constantly  removed,  and  estimated.  An  incomplete  series  of  observations  is- 
published,  which  has  particular  reference  to  the  products  of  respiration.  Thus 
far  the  subject  of  consumption  of  oxygen  has  not  been  considered.  Extended  ob- 
servations by  Dr.  Pettenkofer  will  undoubtedly  settle  many  disputed  questions 
regarding  the  changes  of  the  air  in  respiration.  This  method  was  adapted  to  the 
27 


418  EESPEBATION. 

The  indirect  method  was  first  employed  by  Boussingault, 
but  was  particularly  directed  to  the  exhalation  of  carbonic 
acid.  This  observer  experimented  upon  large  animals,  such 
as  the  horse  or  cow,  in  the  following  way :  Having  first  care- 
fully regulated  the  diet,  so  that  there  was  no  change  in  weight 
during  the  experiments,  he  carefully  weighed  all  that  was 
introduced  as  food  and  drink,  and  all  that  was  discharged 
as  urine  and  feces.  The  excess  in  the  quantity  introduced, 
over  that  discharged  in  the  way  above  mentioned,  represents, 
necessarily,  the  amount  lost  by  the  skin  and  lungs.  By  a 
quantitative  comparison  of  the  elementary  constituents  of  the 
food  and  excrements,  tolerably  accurate  results  were  arrived 
at ;  though  it  must  be  admitted  that  this  method  would  be 
considered  of  little  value,  did  the  results  not  correspond  pretty 
closely  with  those  obtained  by  direct  analysis.1 

Estimates  of  the  absolute  quantities  of  oxygen  consumed, 
or  of  carbonic  acid  produced,  which  are  based  on  analyses  of 
the  inspired  and  expired  air,  calculations  from  the  aver- 
age quantity  of  air  changed  with  each  respiratory  act,  and 
the  average  number  of  respirations  per  minute,  are  by  no 
means  as  reliable  as  analyses  showing  the  actual  changes 
in  the  air,  like  those  of  Eegnault  and  Keiset,  provided  the 
physiological  conditions  be  fulfilled.  When  there  is  so  much 
multiplication  and  calculation,  a  very  slight  and  perhaps 
unavoidable  inaccuracy  in  the  quantities  consumed  or  pro 
duced  in  a  single  respiration  will  make  an  immense  error 
in  the  estimate  for  a  day,  or  even  an  hour. 

Bearing  all  these  sources  of  error  in  mind,  from  the  ex- 
periments of  Yalentin  and  Brunner,  Dumas,  and  others,  a  suf- 
ficiently accurate  approximation  of  the  proportion  of  oxygen 
consumed  by  the  human  subject  may  be  formed.  The  air, 

human  subject  on  a  small  scale  in  1843,  by  Scharling,  but  there  was  no  arrange- 
ment for  estimating  the  quantity  of  oxygen  furnished  (MILNE-EDWARDS,  Physi- 
ologic, tome  ii.,  p.  498,  note.) 

1  BOUSSINGAULT,  Memoires  de  Chimie  Agricole  et  de  Physiologic,  Paris,  1854, 
pp.  1-12. 


CONSUMPTION   OF   OXYGEN.  419 

which  contains,  when  inspired,  20*81  parts  of  oxygen  per 
100,  is  found  on  expiration  to  contain  but  about  16  parts 
per  100.  In  other  words,  the  volume  of  oxygen  absorbed  in 
the  lungs  is  five  per  cent,  or  -^  of  the  volume  of  air  in- 
spired.1 

It  is  interesting  and  useful  to  extend  this  estimate  as  far 
as  possible  to  the  quantity  of  oxygen  absorbed  in  a  definite 
time  ;  for  the  regulation  of  the  supply  of  oxygen  where  many 
persons  are  assembled,  as  in  public  buildings,  hospitals, 
etc.,  is  a  question  of  great  practical  importance.  Assuming 
that  the  average  respirations  per  minute  are  18,  and  that 
with  each  act  20  cubic  inches  of  air  are  changed,  15  cubic 
feet  of  oxygen  are  consumed  in  the  twenty-four  hours,  which 
represents  300  cubic  feet  of  pure  air.  This  is  the  minimum 
quantity  of  air  which  is  actually  used,  making  no  allowance 
for  the  increase  in  the  intensity  of  the  respiratory  processes, 
which  is  liable  to  occur  from  various  causes.  To  meet  all  the 
respiratory  exigencies  of  the  system,  in  hospitals,  prisons,  etc., 
it  has  been  found  necessary  to  allow  at  least  800  cubic  feet 
of  air  for  each  person,  unless  the  situation  is  such  that  the  air 
is  changed  with  unusual  frequency;  for,  beside  the  actual 
loss  of  oxygen  in  the  respired  air,  constant  emanations  from 
both  the  pulmonary  and  cutaneous  surfaces  are  taking  place, 
which  should  be  removed.  In  some  institutions  as  much  as 
2,500  cubic  feet  of  air  is  allowed  to  each  person.2^ 

The  quantity  of  oxygen  consumed  is  subject  to  great 
variations,  depending  upon  temperature,  the  condition  of  the 
digestive  system,  muscular  activity,  etc.  The  following  con- 
clusions, the  results  of  the  observations  of  Lavoisier  and  Se- 
guin,  give  at  a  glance  the  variations  from  the  above-men- 
tioned causes : 3 

1  MILNE-EDWARDS,  Phyxiologie,  tome  ii.,  p.  510. 

2  TODD  and  BOWMAN,  Physiological  Anatomy  and  Physiology  of  Man,  Phila- 
delphia, 1857,  p.  728. 

8  Taken  from  LONGET,  Traite  de  Physiologic,  Paris,  1861,  tome  i.,  p.  526. 
Though  the  absolute  quantities  obtained  by  Lavoisier  and  Seguin  are  not  so  rp- 
liable  as  those  obtained  by  later  observers,  yet  the  accurate  employment  of  the 


420  RESPIRATION. 

"  1.  A  man,  in  repose  sad  fasting,  with  an  external  tem- 
perature of  90°  Fahr.,  consumes  1,465  cubic  inches  of  oxygen 
per  hour. 

"  2.  A  man,  in  repose  and  fasting,  with  an  external  tem- 
perature of  59°  Fahr.,  consume^  1,627  cubic  inches  of  oxygen 
per  hour. 

"  3.  A  man,  during  digestion,  consumes  2,300  cubic 
inches  of  oxygen  per  hour. 

"  4.  A  man,  fasting,  while  he  accomplishes  the  labor  ne- 
cessary to  raise,  in  fifteen  minutes,  a  weight  of  7*343  kil. 
(about  16  Ib.  3  oz.  av.)  to  the  height  of  656  feet,  consumes 
3,874  cubic  inches  of  oxygen  per  hour. 

"  5.  A  man,  during  digestion,  accomplishing  the  labor 
necessary  to  raise,  in  fifteen  minutes,  a  weight  of  7*343  kil. 
(about  16  Ib.  3  oz.  av.)  to  the  height  of  700  feet,  consumes 
5,568  cubic  inches  of  oxygen  per  hour." 

Influence  of  Temperature. — All  who  have  experimented 
on  the  influence  of  temperature  upon  the  consumption  of 
oxygen,  in  the  warm-blooded  animals  and  in  the  human  sub- 
ject, have  noted  a  marked  increase  at  low  temperatures. 
Cold-blooded  animals  always  suffer  a  depression  of  the  vital 
processes  at  low  temperatures,  with  a  corresponding  diminu- 
tion in  the  quantity  of  oxygen  consumed,  until  they  finally 
become  torpid. 

Immediately  after  birth,  the  consumption  of  oxygen  in 
the  warm-blooded  animals  is  relatively  very  slight.  Buffon * 
and  Legallois 2  have  shown  that  just  after  birth,  dogs  and 
other  animals  will  live  for  half  an  hour  or  more  under  water ; 
and  cases  are  on  record  where  life  has  been  restored  in  newly- 
born  children  after  seven,  and,  it  has  been  stated,  after  twenty- 
three  hours  of  asphyxia.  During  the  first  periods  of  exist- 
ence, the  condition  of  the  newly-born  approximates  to  that  of  a 

best  means  of  investigation  at  their  command  leads  us  to  place  every  confidence 
in  the  comparative  results. 

1  MILNE-EDWARDS,  Physiologic,  tome  ii.,  p.  559. 

2  LEGALLOIS,  (Euvres,  Paris,  1824,  tome  i.,  p.  67. 


INFLUENCE    OF   TEMPEKATUKE.  421 

cold-blooded  animal.  The  lungs  are  relatively  very  small,  and 
it  is  some  time  before  they  fully  assume  their  function.  The 
muscular  movements  are  hardly  more  than  is  necessary  to  take 
the  small  amount  of  nourishment  consumed  at  that  period,  and 
nearly  all  of  the  time  is  passed  in  sleep.  There  is  also  very 
little  power  of  resistance  to  low  temperature.  Though  accu- 
rate researches  regarding  the  comparative  quantities  of  oxy- 
gen in  the  venous  and  arterial  blood  of  the  foetus  are  wanting, 
it  has  been  frequently  observed  that  the  difference  in  color  is 
not  as  marked  as  it  is  after  pulmonary  respiration  becomes 
established.  The  direct  researches  of  "W".  F.  Edwards  have 
shown  that  the  absolute  consumption  of  oxygen  by  very 
young  animals  is  very  small ; *  and  the  observations  of  Lcgal- 
lois  on  rabbits,  made  every  five  days  during  the  first  month 
of  existence,  show  a  rapidly  increasing  demand  for  this  prin- 
ciple with  age.2 

Regnault  and  Reiset  have  shown  that  the  consumption 
of  oxygen  is  greater  in  lean  than  in  very  fat  animals,  pro- 
vided they  be  in  perfect  health.  They  have  also  shown  that 
the  consumption  is  much  greater  in  carnivorous  than  in 
herbivorous  animals;  and  in  animals  of  different  sizes,  is 
relatively  very  much  greater  in  those  which  are  very  small. 
In  very  small  birds,  such  as  the  sparrow,  the  proportional 
quantity  of  oxygen  absorbed  was  ten  times  greater  than  in 
the  fowl.3 

In  sleep,  the  quantity  of  oxygen  consumed  is  considerably 


1  De  ^Influence  des  Agens  Physiques  sur  la  Vie,  Paris,  1824,  p.  178  et  seq. 

2  Loc.  oil.    In  his  experiments  on  rabbits,  Legallois  found  that  immmediately 
after  birth  they  would  live  for  fifteen  minutes  deprived  of  air.     "In  asphyxiating 
rabbits  of  different  ages,  for  example,  every  five  days,  from  the  moment  of  birth 
to  the  age  of  one  month,  it  was  constantly  observed  that  the  duration  of  sensa- 
tion, of  voluntary  motion,  in  a  word,  the  signs  of  life,  always  diminished  in  pro- 
portion as  the  animals  advanced  in  age.     Thus,  in  a  rabbit  newly  born,  sensation 
and  voluntary  movements  were  not  extinct  until  the  end  of  about  fifteen  minutes 
of  asphyxia,  while  they  were  extinct  in  less  than  two  minutes  in  a  rabbit  of  the 
age  of  thirty  days."     Pp.  57,  58. 

*  Loc.  cit. 


422  RESPIRATION. 

diminished ;  and  in  hibernation  is  so  small,  that  Spallanzani 
could  not  detect  any  difference  in  the  composition  of  the  air 
in  which  a  marmot,  in  a  state  of  torpor,  had  remained  for 
three  hours.1  In  experiments  on  a  marmot  in  hibernation, 
Regnault  and  Reiset  observed  %  reduction  in  the  quantity  of 
oxygen  consumed  to  about  -^  of  the  normal  standard.2 

It  has  been  shown  by  experiments,  that  the  consumption 
of  oxygen  bears  a  pretty  constant  ratio  to  the  production  of 
carbonic  acid ;  and  as  the  observations  on  the  influence  of 
sex,  number  of  respiratory  acts,  etc.  on  the  activity  of  the 
respiratory  processes,  have  been  made  chiefly  with  reference 
to  the  carbonic  acid  exhaled,  we  will  consider  these  influences 
in  connection  with  the  products  of  respiration. 

Experiments  on  the  effect  of  increasing  the  proportion  of 
oxygen  in  the  air  have  led  to  varied  results  in  the  hands  of 
different  observers.  Regnault  and  Reiset,  whose  observa- 
tions on  this  point  are  generally  accepted,  did  not  discover 
any  increase  in  the  consumption  of  oxygen  when  this  gas  was 
largely  in  excess. 

The  results  of  confining  an  animal  in  an  atmosphere  com- 
posed of  21  parts  of  oxygen  and  79  parts  of  hydrogen  are 
very  curious  and  instructive.  "When  hydrogen  is  thus  sub- 
stituted for  the  nitrogen  of  the  air,  the  consumption  of  oxygen 
is  largely  increased.  Regnault  and  Reiset  attribute  this  to 
the  superior  refrigerating  power  of  the  hydrogen ;  but  a  more 
rational  explanation  would  seem  to  be  in  its  superior  diffusi- 
bility.  Hydrogen  is  the  most  diffusible  of  all  gases;  and 
when  introduced  into  the  lungs  in  the  place  6f  the  nitrogen 
of  the  air,  the  vitiated  air,  charged  with  carbonic  acid,  is 
undoubtedly  more  readily  removed  from  the  deep  portions 
of  the  lungs,  giving  place  to  the  mixture  of  hydrogen  and 
oxygen ;  and  it  is  probably  for  this  reason  that  the  quantity 
of  oxygen  consumed  is  increased.  It  is  probable  that  the 

1  SPALLANZANI,  Memoires  sur  la  Respiration,  traduites  par  SENEBIER,  Geneve, 
1803,  p.  334. 

2  Op.  cit.,  p.  442. 


INFLUENCE   OF  TEMPERATURE.  423 

nitrogen  of  the  air  plays  an  important  part  in  the  phenomena 
of  respiration  by  virtue  of  its  degree  of  diffusibility. 

In  view  of  the  great  variations  in  the  consumption  of 
oxygen  dependent  on  different  physiological  conditions,  such 
as  digestion,  exercise,  temperature,  etc.,  it  is  impossible  to  fix 
upon  any  number  which  will  represent,  even  approximative^, 
the  average  quantity  consumed  per  hour.  The  estimate 
arrived  at  by  Longet,1  from  a  comparison  of  the  results  ob- 
tained by  different  reliable  observers,  is  perhaps  as  near  the 
truth  as  possible.  This  estimate  puts  the  hourly  consumption 
at  from  1,220  to  1,525  cubic  inches,  "  in  an  adult  male,  during 
repose  and  in  normal  conditions  of  health  and  temperature." 

In  passing  through  the  lungs,  the  air,  beside  losing  a 
proportion  of  its  oxygen,  undergoes  the  following  changes : 

1.  Increase  in  temperature. 

2.  Gain  of  carbonic  acid. 

3.  Gain  of  watery  vapor. 

4.  Gain  of  ammonia. 

5.  Gain  of  a  small  quantity  of  organic  matter. 

6.  Gain,  and  occasionally  loss,  of  nitrogen. 

The  elevation  in  temperature  of  the  air  which  has  passed 
through  the  lungs  has  been  carefully  observed  by  Dr.  Gre- 
hant.2  He  found  that  with  an  external  temperature  of  72°, 
respiring  17  times  per  minute,  the  air  taken  in  by  the  nares 
and  expired  by  the  mouth,  through  an  apparatus  containing 
a  thermometer  carefully  protected  from  external  influences, 
marked  a  temperature  of  95*4°.  Taking  in  the  air  by  the 
mouth,  the  temperature  of  the  expired  air  was  93°.  At  the 
commencement  of  the  expiration,  Dr.  Grehant  noted  a  tem- 
perature of  94°.  After  a  prolonged  expiration,  the  temper- 
ature was  96°.  In  these  observations  the  temperature  taken 
beneath  the  tongue  was  98°. 

1  Op.  cit.,  p.  531. 

2  GREHANT,  Rcchcrclws  Physiques  sur  la  -Respiration  de  VHomme. — Journal  d< 
FAnatomie  et  de  la  Physiologic,  1864,  tome  i,  p.  546. 


4:24  RESPIRATION. 

Valentin  had  previously  made  experiments  on  this  point, 
and  put  the  temperature  of  the  expired  air  a  little  higher, 
i.  <?.,  about  99°,  with  an  external  temperature  of  68°.  He 
also  showed  that  the  temperature  of  the  surrounding  atmos- 
phere exerted  an  important  influence  on  the  temperature  of 
the  expired  air.  In  an  observation  made  in  winter,  with  an 
external  temperature  of  18°,  the  temperature  of  the  expired 
air  was  only  85'S0.1 

Exhalation  of  Carbonic  Acid. — The  production  of  car- 
bonic acid  in  the  respiratory  process  is  as  universal  as  the 
consumption  of  oxygen.  Experiments  have  shown  that  all 
animals  during  life  exhale  this  principle,  as  well  as  all  tis- 
sues, so  long  as  they  retain  their  irritability.  This  takes 
place,  not  only  when  the  animals  or  tissues  are  placed  in  an 
atmosphere  of  oxygen,  or  common  air,  but,  as  was  observed 
by  Spallanzani,2  in  an  atmosphere  of  pure  nitrogen  or  hydro- 
gen. This  fact  has  since  been  noted  by  "W.  F.  Edwards,  J. 
Miiller,  G.  Liebig,  and  others. 

The  study  of  the  exhalation  of  carbonic  acid  presents  sev- 
eral problems  of  great  physiological  interest : 

1.  What  is  the  absolute  quantity  of  carbonic  acid  exhaled 
by  the  lungs  in  a  given  time  1 

2.  What  are  the  variations  in  the  exhalation  of  this  prin- 
ciple due  to  physiological  influences  ? 

3.  What  is  the  relation  between  the  quantity  of  carbonic 
acid  produced  and  the  quantity  of  oxygen  consumed  ? 

On  account  of  the  variations  in  the  quantities  of  carbonic 
acid  exhaled  at  different  periods  of  the  day,  and  particularly 
the  great  influence  of  the  rapidity  of  the  respiratory  move- 
ments, it  is  exceedingly  difficult  to  fix  upon  any  number 
which  will  represent  the  average  proportion  of  this  gas  con- 
tained in  the  expired  air.  The  same  influences  were  found 
affecting  the  consumption  of  oxygen ;  and  the  same  difficulties 

1  GREHANT,  Rtcherches  Physiques  sur  la  Respiration  de  V Homme.— Journal  de 
PAnatomie  et  de  la  Physiologic,  1864,  tome  i.,  p.  545. 
3  Op.  dt.,  p.  343. 


EXHALATION   OF   CARBONIC   ACID.  425 

were  experienced  in  forming  an  estimate  of  the  proportion 
of  this  gas  consumed.  As  we  assumed,  after  a  comparison 
of  the  results  obtained  by  different  observers,  that  the  vol- 
ume of  oxygen  consumed  is  about  five  per  cent,  of  the  entire 
volume  of  air,  it  may  be  stated  as  an  approximation,  that  in 
the  intervals  of  digestion,  in  repose,  and  under  normal  con- 
ditions as  regards  the  frequency  of  the  pulse  and  respiration, 
the  volume  of  carbonic  acid  exhaled  is  about  four  per  cent, 
of  the  volume  of  the  expired  air.1  As  the  volume  of  the  oxy- 
gen which  enters  into  the  composition  of  a  definite  quantity  of 
carbonic  acid  is  precisely  equal  to  the  volume  of  the  car- 
bonic acid,  it  is  seen  that  a  certain  quantity  of  oxygen  disap- 
pears in  respiration,  and  is  not  represented  in  the  carbonic 
acid  exhaled. 

There  are  great  differences  in  the  proportion  of  carbonic 
acid  in  the  expired  air,  depending  upon  the  time  during 
which  the  air  has  remained  in  the  lungs.  This  interesting 
point  has  been  studied  by  Yierordt,  in  a  series  of  94  experi- 
ments made  upon  his  own  person,  with  the  following  results : 2 

"  When  the  respirations  are  frequent,  the  quantity  of  car- 
bonic acid  expelled  at  each  expiration  is  much  less  than  in  a 
slow  expiration ;  but  the  quantity  of  carbonic  acid  produced 
during  a  given  time  by  frequent  respirations  is  greater  than 
that  which  is  thrown  off  by  slow  expirations."  3 

The  air  which  escapes  during  the  first  period  of  an  expi- 
ration is  naturally  less  rich  in  carbonic  acid  than  that  which 
is  last  expelled  and  comes  directly  from  the  deeper  portions 
of  the  lungs.  Dividing,  as  nearly  as  possible,  the  expiration 
into  two  equal  parts,  Yierordt  found,  as  the  mean  of  twenty- 

1  MILNE-EDWARDS,  Physiologic,  tome  ii.,  p.  507.  This  approximation  is  taken 
from  the  observations  of  Valentin  and  Brunner,  Dalton,  Prout,  Apjohn,  Coathupe, 
Horn,  and  Vierordt.  The  experiments  of  Vierordt  are,  perhaps,  entitled  to  the 
most  credit,  as  he  has  studied  very  carefully  the  influence  of  the  frequency  of  res- 
piration upon  the  quantity  of  carbonic  acid  exhaled. 

a  Cited  in  MILNE-EDWARDS,  Physiologic,  tome  ii.,  p«  574,  and  BERARD,  Cours 
do  Physiologic,  tome  iii.,  p.  349. 

s  BERARD,  loc.  cit. 


426  RESPIRATION. 

one  experiments,  a  percentage  of  3 '72  in  the  first  part  of  the 
expiration,  and  5*44  in  the  second  part.1 

Temporary  arrest  of  the  respiratory  movements,  as  we 
should  expect,  has  a  marked  influence  in  increasing  the  pro- 
portion of  carbonic  acid  in  the  ^xpired  air ;  though  the  abso- 
lute quantity  exhaled  in  a  given  time  is  diminished.  In  a 
number  of  experiments  on  his  own  person,  Vierordt  ascer- 
tained that  the  percentage  of  carbonic  acid  becomes  uniform 
in  all  parts  of  the  respiratory  organs,  after  holding  the 
breath  for  40  seconds.  Holding  the  breath  after  an  ordinary 
inspiration  for  20  seconds,  the  percentage  of  carbonic  acid 
in  the  expired  air  was  increased  1*73  over  the  normal  stand- 
ard ;  but  the  absolute  quantity  exhaled  was  diminished  by 
2'642  cubic  inches.  After  taking  the  deepest  possible  inspi- 
ration, and  holding  the  breath  for  100  seconds,  the  percent- 
age wras  increased  3*08  above  the  normal  standard ;  but  the 
absolute  quantity  was  diminished  more  than  14  cubic  inches.2 
Allen  and  Pepys  state  that  air  which  has  passed  9  or  10  times 
through  the  lungs  contains  9*5  per  cent,  of  carbonic  acid.3  - 

Yierordt  gives  the  following  formula  as  representing  the 
influence  of  the  frequency  of  the  respirations  on  the  produc- 
tion of  carbonic  acid  :  Taking  2'5  parts  per  hundred  as  rep- 
resenting the  constant  value  of  the  gas  exhaled  by  the  blood, 
the  increase  over  this  proportion  in  the  expired  air  is  in 
exact  ratio  to  the  duration  in  the  contact  of  the  air  and 
blood.  This,  though  it  may  hold  good  in  many  instances, 
seems  rather  an  excessive  refinement.4 

1  LEHMANN,  Physiological  Chemistry,  Philadelphia,  1855,  vol.  ii.,  p.  439. 

2  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iv.,  part  1,  p.  352. 

3  Ibid. 

4  The  following  table  gives  at  a  glance  the  most  important  results  of  these 
experiments : 

Proportion  of  Carbonic  Acid.  Number  of  Respirations  per  Minute. 

5-7  per  100  parts  of  air 6 

41        "        "       "       12 

3-3        "        "        "        24 

2-9        •'        "        "       48 

2-T       "       "       "       96 


EXHALATION   OF   CAKBONIC   ACID.  427 

The  absolute  quantity  of  carbonic  acid  exhaled  in  a  given 
time  is  a  more  important  subject  of  inquiry  than  the  propor- 
tion contained  in  the  expired  air ;  for  the  latter  is  constant- 
ly varying  with  every  modification  in  the  number  and  ex- 
tent of  the  respiratory  acts,  and  the  volume  of  breathing 
air  is  subject  to  great  fluctuations,  and  is  very  difficult  of 
determination.  The  direct  method,  in  which  the  actual 
products  of  respiration  are  collected  and/  estimated,  has  led 
to  very  important  results,  which  have  been  confirmed  to  a 
certain  extent  by  Boussingault,  Barral,  and  others  who  have 
employed  the  indirect  method.  It  is  by  the  direct  method, 
in  the  hands  of  Regnault  and  Reiset,  Andral  and  Gavarret, 
and  more  recently  Dr.  Edward  Smith,  that  we  have  learned 
so  much  regarding  the  physiological  variations  in  the  prod- 
ucts of  respiration ;  one  of  the  most  important  considerations 
connected  with  the  subject. 

Among  the  most  reliable  observations  on  the  quantity  of 
carbonic  acid  exhaled  by  the  human  subject  in  a  definite 
time,  and  the  variations  to  which  it  is  subject,  are  those  of 
Andral  and  Gavarret,1  and  Dr.  Edward  Smith.8  The  obser- 
vations of  Lavoisier  and  Seguin,  Prout,  Davy,  Dumas,  Allen 
and  Pepys,  Scharling,  and  others,  have  none  of  them  seemed 
to  fulfil  the  necessary  experimental  conditions  so  completely; 
Schaiiing's  method  was  to  enclose  his  subject  in  a  tight  box, 
with  a  capacity  of  about  27  cubic  feet,  to  which  air  was  con- 
stantly supplied;  but  the  observations  were  comparatively 
few,  being  made  on  only  six  persons.  In  his  observations, 
the  quantities  of  gas  exhaled  must  have  been  considerably 
modified  by  the  elevation  of  temperature  and  exhalation  of 
moisture  in  so  small  a  space.3  The  mental  condition  of  the 

1  Recherches  sur  la  Quantite  d'Acide  Carbonique  exhale  par  les  Poumons  dan* 
VEspece Humaine. — Annalesde  Chimie etde Physique,  3meserie,tomeviii.,p.  129. 

a  EDWARD  SMITH,  Experimental  Inquiries  into  the  Chemical  and  other  Phenom- 
ena of  Respiration,  and  their  Modifications  by  various  Physical  Agencies  (Phi- 
losophical Transactions,  1859,  p.  681) ;  and  On  the  Action  of  Foods  upon  the 
Respiration  during  the  Primary  Processes  of  Digestion  (Ibid.,  p.  715). 

3  Annales  de  Chim.  et  de  Phys.,  tome  viii.,  p.  488.     Scharling  recognized  the 


428  RESPIRATION. 

subject  of  an  experiment  has  an  influence  upon  the  products 
of  respiration,  and  the  function  is  sometimes  modified  from 
the  mere  fact  that  an  experiment  is  being  performed ;  an  in- 
fluence which  Scharling  did  not  fail  to  recognize,  but  which 
frequently  cannot  be  guarded  against. 

The  observations  of  Andral  and  Gavarret  were  made  on 
sixty-two  persons  of  both  sexes  and  different  ages,  and  under 
absolutely  identical  conditions  as  regards  digestion,  time  of 
the  day,  barometric  pressure,  and  temperature.  The  prod- 
ucts of  respiration  were  collected  in  the  following  way : 
A  thin  mask  of  copper  covering  the  face,  and  large  enough 
to  contain  an  entire  expiration,  was  fitted  to  the  face  by 
its  edges,  which  were  provided  with  India-rubber,  so  as  to 
make  it  air-tight.  At  the  upper  part  was  a  plate  of  glass  for 
the  admission  of  light,  and  at  the  lower  part  an  opening, 
which  allowed  the  entrance  of  air,  but  was  provided  with  a 
valve  preventing  its  escape.  By  another  opening  the  mask 
was  connected  by  a  rubber  tube  with  three  glass  balloons,  ca- 
pable of  holding  8,544  cubic  inches,  in  which  a  vacuum  was 
previously  established.  With  the  mask  fixed  upon  the  face, 
and  a  stop-cock  opened,  connected  with  the  balloons,  so  as  to 
graduate  the  current  of  air,  the  subject  respires  freely  in  the 
current  which  comes  from  the  exterior  into  the  receivers.  In 
this  way,  though  the  quantity  of  air  respired  is  not  measured, 
the  vacuum  in  the  receivers  draws  in  the  products  of  respira- 
tion. The  current  will  continue  for  from  8  to  13  minutes, 
and  is  so  regulated  that  the  air  is  respired  but  once.  The 
quantity  of  carbonic  acid  in  the  receivers  represents  the 
quantity  produced  during  the  time  that  the  experiment  has 
been  going  on. 

By  carefully  fulfilling  all  the  physiological  conditions, 

necessity  of  guarding  against  the  influence  of  elevation  of  temperature  and  accu- 
mulation of  moisture,  and  attempted  to  remove  the  latter  by  introducing  a  vessel 
of  sulphuric  acid.  His  greatest  difficulty  was  in  the  analyses  of  the  air.  Though 
the  results  obtained  are  valuable,  the  process  cannot  claim  the  accuracy  attained 
by  Andral  and  Gavarret. 


EXHALATION   OF   CAKBONIC   ACID.  429 

regulating  the  number  of  respirations,  as  far  as  possible,  to 
the  normal  standard,  different  observations  on  the  same  sub- 
ject, at  different  times,  under  the  same  conditions,  were  at- 
tended with  results  so  nearly  identical,  as  to  give  every  con- 
fidence in  the  accuracy  of  the  process.  But  even  then,  these 
observers  recognized  such  immense  variations  in  the  exhala- 
tion of  carbonic  acid  with  the  constantly  varying  physiologi- 
cal conditions,  that  they  did  not  feel  justified  in  taking  their 
observations  as  the  basis  for  calculations  of  the  entire  quantity 
exhaled  in  the  twenty-four  hours. 

The  results  of  these  observations  on  the  male,  between  the 
ages  of  sixteen  and  thirty,  between  1  and  2  P.M.,  under  iden- 
tical conditions  of  the  digestive  and  muscular  systems,  each 
experiment  lasting  from  eight  to  thirteen  minutes,  showed  an 
exhalation  of  about  1,220  cubic  inches  of  carbonic  acid  per 
hour. 

Dr.  Edward  Smith,1  in  his  elaborate  paper  on  the  phe- 
nomena of  respiration,  employed  a  very  rigorous  method  for 
the  estimation  of  the  carbonic  acid  exhaled.  He  used  a 
mask,  fitting  closely  to  the  face,  which  covered  only  the  air- 
passages.  The  air  was  admitted  after  being  measured  by 
passing  through  an  ordinary  dry  gas-meter.  The  expired 
air  was  passed  through  a  drying  apparatus,  and  the  carbonic 
acid  absorbed  by  a  solution  of  potash,  arranged  in  a  number 
of  layers,  so  as  to  present  a  surface  of  about  700  square  inches, 
and  carefully  weighed.  This  apparatus  was  capable  of  col- 
lecting all  the  carbonic  acid  exhaled  in  an  hour.  The  esti- 
mate was  made  for  18  waking  hours  and  6  hours  of  sleep. 
The  observations  for  the  18  hours  were  made  on  four  persons, 
namely :  Dr.  Smith,  set.  38  years,  weighing  196  pounds,  6 
feet  high,  with  a  vital  capacity  of  280  cubic  inches ;  Mr. 
Moul,  set.  48  years,  5  feet  9J  inches  high,  175  pounds 
weight ;  Dr.  Murie,  set.  26  years,  5  feet  7£  inches  high,  133 
pounds  weight,  vital  capacity  250  cubic  inches ;  Prof.  Frank- 
land,  set.  33  years,  5  feet  10J  inches  high,  and  136  pounds 

1  Loc.  tit. 


430  RESPIRATION. 

weight.     Breakfast  was  taken  at  8J-  A.M.,  dinner  at  1J,  tea  at 

5  J,  and  supper  at  8J  P.M.     The  observations  occupied  ten  min- 
utes, and  were  made  every  hour  and  half-hour  for  18  hours. 
The  average  for  the  18  hours  gave  20,082  cubic  inches  of 
carbonic  acid  for  the  whole  peiiod.     Observations  during  the 

6  hours  of  sleep  showed  a  total  exhalation  of  4,126  cubic 
inches.     This,  added  to  the  quantity  exhaled  during  the  day, 
gives  as  the  total  exhalation  in  the  twenty-four  hours,  during 
complete  repose,  24,208  cubic  inches  (about  14-24  cubic  feet), 
containing  7*144  oz.  av.  of  carbon.1 

Considering  the  great  variations  in  the  exhalation  of  car- 
bonic acid,  this  estimate  can  be  nothing  more  than  an  ap- 
proximation. One  of  the  great  modifying  influences  is  mus- 
cular exertion,  by  which  the  production  of  carbonic  acid  is 
largely  increased.  This  would  indicate  a  larger  quantity 
during  ordinary  conditions  of  exercise,  and  a  much  larger 
quantity  in  the  laboring  classes.  Dr.  Smith  gives  the  fol- 
lowing approximate  estimates  of  these  differences : 2 

In  quietude 7'144  oz.  av.  of  carbon. 

Non-laborious  class 8'68         "  " 

Laborious  class ll'T 

In  studying  the  variations  in  the  exhalation  of  carbonic 
acid,  important  information  has  been  derived  from  experi- 
ments by  many  observers  on  the  inferior  animals,  as  well  as 
from  the  observations  of  Dumas,  Prout,  Scharling,  and  others 
on  the  human  subject.  The  principal  conditions  which 
influence  the  exhalation  of  this  principle  are : 

Age  and  sex ;  activity  or  repose  of  the  digestive  system ; 
form  of  diet ;  sleep ;  muscular  activity ;  fatigue ;  moisture, 
and  surrounding  temperature ;  season  of  the  year. 

1  Op.  cit.,  p.  692.  In  these  calculations  there  is  a  slight  arithmetical  error; 
but  it  makes  a  difference  of  only  40  cubic  inches  of  gas  in  the  estimate  for  the  24 
hours.  In  the  original  paper,  the  quantity  is  given  by  weight.  We  have  re- 
duced it  to  cubic  inches,  assuming  that  100  cubic  inches  of  gas  weigh  47  26  grains. 

a  Op.  cit.,  p.  693. 


INFLUENCE   OF  AGE.  431 

Influence  of  Age. — In  treating  of  the  consumption  of 
oxygen,  it  was  stated  that  during  the  first  few  days  of  extra- 
uterine  existence,  the  demand  for  oxygen  on  the  part  of  the 
system  is  very  slight.  At  this  period  there  is  a  correspond- 
ingly feeble  exhalation  of  carbonic  acid.  It  is  well  known 
that  during  the  first  hours  and  days  after  birth  the  new 
being  has  little  power  of  generating  heat,  needs  constant 
protection  from  changes  in  temperature,  and  the  volun- 
tary movements  are  very  imperfect.  During  the  first  few 
days,  indeed,  the  infant  does  little  more  than  sleep  and  take 
the  small  quantity  of  colostrum  which  is  furnished  by  the 
mammary  glands  of  the  mother.  "While  the  animal  functions 
are  so  imperfectly  developed,  and  until  the  nourishment  be- 
comes more  abundant  and  the  child  begins  to  increase  rapidly 
in  weight,  the  quantity  of  carbonic  acid  exhaled  is  very  small. 

After  the  respiratory  function  becomes  fully  established, 
it  is  probable,  from  the  greater  number  of  respiratory  move- 
ments in  early  life,  that  the  production  of  carbonic  acid,  in 
proportion  to  the  weight  of  the  body,  is  greater  in  infancy 
than  in  adult  life.  Direct  observations,  however,  are  wanting 
on  this  point. 

The  observations  of  Andral  and  G-avarret 1  show  the  com- 
parative exhalation  of  carbonic  acid  in  the  male,  from  the  age 
of  twelve  to  eighty-two,  and  give  the  results  of  a  single  obser- 
vation at  the  age  of  one  hundred  and  two  years.  They  show 
an  increase  in  the  absolute  quantity  exhaled  from  the  age  of 
twelve  to  thirty-two ;  a  slight  diminution  from  thirty-two  to 
sixty ;  and  a  considerable  diminution  from  sixty  to  eighty- 
two.  These  results  are  given  in  the  following  table : 

Carbonic  acid  exhaled  per  hour. 

In  boys  from  twelve  to  sixteen  years 915  cubic  inches. 

In  young  men  from  seventeen  to  nineteen  years 1,220     "        " 

In  men  from  twenty-five  to  thirty-two  years 1,343     "        " 

In  men  from  thirty-two  to  sixty  years 1,220     "         " 

In  men  from  sixty-three  to  eighty-two  years 933     "         " 

In  an  old  man  of  one  hundred  and  two  years 671     "        ** 

1Loc.  cit. 


432  EESPIEATION. 

Taking  into  consideration  the  increase  in  the  weight  of 
the  body  with  age,  it  is  evident  that  the  respiratory  activity 
is  much  greater  in  youth  than  in  adult  life.  Andral  and 
Gavarret  do  not  give  the  weight  of  the  subjects  of  their 
observations,  but  as  the  weight  generally  does  not  diminish 
after  maturity,  there  can  be  no  doubt  that  there  is  a  rapid 
diminution  in  the  relative  quantity  of  carbonic  acid  produced 
in  old  age. 

Scharling,  in  a  series  of  observations  on  a  boy  nine  years 
of  age,  weighing  48*5  pounds,  an  adult  of  twenty-eight,  and 
one  of  thirty-five  years,  the  latter  weighing  163*6  pounds, 
showed  that  the  respiratory  activity  in  the  child  was  nearly 
twice  as  great,  in  proportion  to  his  weight,  as  the  average  in 
the  adults.1  It  is  seen  from  the  observations  of  Andral  and 
Gavarret,  that  the  absolute  increase  in  the  exhalation  of  car- 
bonic acid  from  childhood  to  adnlt  life  is  very  slight  in  com- 
parison with  the  natural  increase  in  the  weight  of  the  body ; 
showing  that,  proportionately,  the  exhalation  of  carbonic  acid 
is  greater  in  early  life. 

Influence  of  Sex. — All  observers  have  found  a  marked 
difference  between  the  sexes,  in  favor  of  the  male,  in  the 
proportion  of  carbonic  acid  exhaled.  Andral  and  Gavarret 
noted  an  absolute  difference  of  about  forty-five  cubic  inches 
per  hour,  but  did  not  take  into  consideration  the  difference 
in  the  weight  of  the  body.  Scharling,  taking  the  proportion 
exhaled  to  the  weight  of  the  body,  noted  a  marked  difference 
in  favor  of  the  male. 

The  difference  in  the  degree  of  muscular  activity  in  the 
sexes  is  sufficient  to  account  for  the  greater  evolution  of  car- 
bonic acid  in  the  male,  for  this  principle  is  exhaled  in  pro- 

1  SCHARLING,  Recherches  sur  la  Quantite  d'Acide  Carbomque  expire  par  VHomme. 
Annales  de  Chimie  et  de  Physique,  3me  serie,  tome  viii.,  p.  486. 

Taking  the  proportion  of  carbonic  acid  exhaled  per  hour  to  the  weight,  in 
the  man  28  years  of  age,  as  1,  in  the  man  35  years  of  age  the  proportion  was  1'14, 
and  in  the  boy  9£  years  of  age,  2'07.  P.  489. 


INFLUENCE   OF   DIGESTION.  433 

portion  to  the  muscular  development  of  the  individual ;  but 
there  is  an  important  difference  connected  with  the  variations 
with  age,  which  depends  upon  the  condition  of  the  generative 
system  of  the  female. 

The  absolute  increase  in  the  evolution  of  carbonic  acid 
with  age  in  the  female  is  arrested  at  the  time  of  puberty, 
and  remains  stationary  during  the  entire  menstrual  period, 
provided  the  menstrual  now  occur  with  regularity.  During 
this  time,  the  average  exhalation  per  hour  is  714  cubic  inches. 
After  the  cessation  of  the  menses,  the  quantity  gradually 
increases,  until  at  the  age  of  sixty  it  amounts  to  915  cubic 
inches  per  hour.  From  the  age  of  sixty  to  eighty-two,  the 
quantity  diminishes  to  793,  and  finally  to  670  cubic  inches. 

When  the  menses  are  suppressed,  there  is  an  increase  in 
the  exhalation  of  carbonic  acid,  which  continues  until  the  flow 
becomes  reestablished.  In  a  case  of  pregnancy  the  exhalation 
was  increased  to  about  885  cubic  inches.1 

Influence  of  Digestion. — Almost  all  observers  agree  that 
the  exhalation  of  carbonic  acid  is  increased  during  digestion. 
Lavoisier  and  Seguin  found  that  in  repose  and  fasting,  the 
quantity  exhaled  per  hour  was  1,210  cubic  inches ;  which  was 
raised  to  1,800  and  1,900  during  digestion.3  Numerous  ex- 
periments on  animals  have  confirmed  this  statement.  A  very 
interesting  series  of  observations  on  this  point  was  made  by 
Yierordt  upon  his  own  person.  Taking  his  dinner  at  from 
12*30  to  1  P.  M.,  having  noted  the  frequency  of  the  pulse 
and  respirations  and  the  exhalation  of  carbonic  acid  at  12, 
he  found  at  2  p.  M.  the  pulse  and  respirations  increased  in 
frequency,  the  volume  of  expired  air  augmented,  and  that 
the  carbonic  acid  exhaled  had  increased  from  15*77  to  18'22 
cubic  inches  per  minute.  In  order  to  ascertain  that  this 

1  The  above  facts,  showing  the  peculiar  influence  of  the  condition  of  the  genera- 
tive organs  in  the  female,  are  among  the  most  important  results  of  the  observa- 
tions of  Andral  and  Gavarret.  Loc.  cit. 

a  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iv.,  part  i.,  pp.  346,  347. 
28 


434  RESPIRATION. 

variation  did  not  depend  upon  the  time  of  day,  inde- 
pendently of  the  digestive  process,  he  made  a  comparison  at 
12  M.,  at  1  and  at  2  p.  M.,  without  taking  food,  which  showed 
no  notable  variation,  either  in  the  pulse,  number  of  respira- 
tions, volume  of  expired  air,  .or  quantity  of  carbonic  acid 
exhaled.1 

It  is  unnecessary  to  cite  other  observations  on  this  point, 
unless  we  mention  those  of  Prout  and  Coathupe,  which 
seemed  to  show  a  diminution  in  the  exhalation  of  carbonic 
acid  during  digestion.  Dr.  John  Reid,  in  the  Cyclopaedia 
of  Anatomy  and  Physiology r,  points  out  the  source  of  error 
in  these  observations.2  Prout  did  not  estimate  the  actual 
quantity  of  gas  exhaled,  but  only  its  proportion  in  the  ex- 
pired air ;  and  it  has  been  demonstrated  that  in  digestion  the 
volume  of  the  expirations  is  notably  increased.  Coathupe, 
in  the  observations  on  his  own  person,  took  a  pint  of  wine 
with  his  dinner.  As  it  has  been  shown  by  experiment  that 
alcohol  has  the  effect  of  rapidly  reducing  the  exhalation  of 
carbonic  acid,  this  observation  does  not  represent  the  simple 
influence  of  digestion. 

There  can  be  no  doubt,  then,  that  the  exhalation  of  car- 
bonic acid  is  notably  increased  during  the  functional  activity 
of  the  digestive  system. 

The  effect  of  inanition  is  to  gradually  diminish  the  exha- 
lation of  carbonic  acid.  This  fact  was  long  since  demon- 
strated by  Spallanzani  on  caterpillars,  and  Marchand  on 
frogs;  but  observations  on  the  warm-blooded  animals  are 
more  applicable  to  the  human  subject.  Bidder  and  Schmidt 
noted  the  daily  production  of  carbonic  acid  in  a  cat  which 
was  subjected  to  eighteen  days  of  inanition,  at  the  end  of 
which  time  it  died.  The  quantity  diminished  gradually  from 
day  to  day,  until  just  before  death  it  was  reduced  a  little 
more  than  one-half.  Dr.  Smith8  noted  in  his  own  person 

1  Cyclopaedia,  of  Anatomy  and  Physiology,  vol.  iv.,  part  i.,  pp.  346,  347. 

2  Ibid.,  article  Respiration. 

3  Op.  dt.,  p.  696. 


INFLUENCE   OF  DIET.  435 

the  influence  of  a  fast  of  twenty-seven  hours.  There  was  a 
marked  diminution  in  the  quantity  of  air  respired,  in  the 
quantity  of  vapor  exhaled,  in  the  number  of  respirations,  and 
in  the  rapidity  of  the  pulse.  The  exhalation  of  carbonic  acid 
was  diminished  one-fourth.  An  interesting  point  in  this 
observation  was  the  fact  that  the  quantity  was  as  small  four 
and  a  half  hours  after  eating,  as  at  the  end  of  the  twenty- 
seven  hours.  "  An  increase  of  carbonic  acid  in  the  absence 
of  food,  at  or  near  the  period  when  it  is  usually  increased  by 
food,"  was  also  noted  in  the  experiment  of  Dr.  Smith. 

Influence  of  Diet. — Regnault  and  Reiset,  in  their  experi- 
ments on  animals,  studied  the  effect  of  different  kinds  of  diet 
upon  the  relations  of  the  quantity  of  oxygen  absorbed  to  the 
carbonic  acid  exhaled.  About  the  only  conclusive  and  ex- 
tended series  of  investigations  on  the  influence  of  diet  upon 
the  absolute  quantity  of  carbonic  acid  exhaled  are  those 
of  Dr.  Smith.  This  observer  made  a  large  number  of 
experiments  on  the  influence  of  various  kinds  of  food,  and 
extended  his  inquiries  into  the  influence  of  certain  beverages, 
such  as  tea,  coffee,  cocoa,  malt  and  fermented  liquors.1  We 
have  already  fully  described  the  method  employed  in  these 
experiments,  and  the  conclusions,  which  are  of  great  interest 
and  importance,  are  very  exact  and  reliable. 

Dr.  Smith  divides  food  into  two  classes,  one  which  in- 
creases the  exhalation  of  carbonic  acid,  which  he  calls  respi- 
ratory excitants,  and  the  other,  which  diminishes  the  exhala- 
tion, which  he  calls  non-exciters. 

The  following  are  the  results  of  a  large  number  of  care- 
fully conducted  observations  upon  four  persons : 

"  The  excito-respiratory  are  nitrogeneous  food,  milk  and 
its  components,  sugars,  rum,  beer,  stout,  the  cereals,  and 
potato. 

"  The  non-exciters  are  starch,  fat,  certain  alcoholic  corn- 

1  On  the  Action  of  Foods  on  the  Respiration  during  the  Primary  Processes  of 
Digestion.  'Philosophical  Transactions,  1859,  p.  715 


4:36  .  KESPIEATIOK. 

pounds,  the  volatile  elements  of  wines  and  spirits,  and  coffee 
leaves. 

"  Kespiratory  excitants  have  a  temporary  action ;  but  the 
action  of  most  of  them  commences  very  quickly,  and  attains 
its  maximum  within  one  hour* 

"  The  most  powerful  respiratory  excitants  are  tea  and 
sugar ;  then  coffee,  rum,  milk,  cocoa,  ales,  and  chicory ;  then 
casein  and  gluten,  and  lastly,  gelatin  and  albumen.  The 
amount  of  action  was  not  in  uniform  proportion  to  their 
quantity.  Compound  aliments,  as  the  cereals,  containing 
several  of  these  substances,  have  an  action  greater  than  that 
of  any  of  their  elements. 

"  Most  respiratory  excitants,  as  tea,  coffee,  gluten,  and 
casein,  cause  an  increase  in  the  evolution  of  carbon  greater 
than  the  quantity  which  they  supply,  whilst  others,  as  sugar, 
supply  more  than  they  evolve  in  this  excess,  that  is,  above 
the  basis.  No  substance  containing  a  large  amount  of  car- 
bon evolves  more  than  a  small  portion  of  that  carbon  in  the 
temporary  action  occurring  above  the  basis  line,  and  hence 
a  large  portion  remains  unaccounted  for  by  these  experi- 
ments." 

The  comparative  observations  of  Dr.  Smith  upon  the  four 
persons  who  were  the  subjects  of  experiment  demonstrated 
one  .very  important  fact :  namely,  that  the  action  of  different 
kinds  of  food  upon  respiration  is  modified  by  idiosyncrasies, 
and  the  tastes  of  different  individuals.  For  example,  in  ex- 
periments on  his  own  person,  certain  articles  which  were 
agreeable  to  him  excited  the  exhalation  of  carbonic  acid ;  but 
in  experimenting  with  the  same  articles  upon  Mr.  Moul,  to 
whom  they  were  distasteful,  he  found  the  respiratory  action 
diminished. 

Quite  a  number  of  observers  have  noted  the  influence  of 
alcohol  upon  the  products  of  respiration ;  but  the  results  of 
experiments  have  not  been  entirely  uniform.  Prout  ob- 
served a  constant  diminution  in  the  quantity  of  carbonic  acid 
exhaled,  under  the  influence  of  alcohol.  This  has  been  confirm 


INFLUENCE   OF   DIET.  437 

ed  by  the  observations  of  Horn,  Yierordt,  and  many  others ;  but 
Hervier  and  Saint-Lager  assert  that  the  use  of  alcohol  increases 
the  exhalation  of  carbonic  acid.1  In  the  experiments  of  Prout, 
a  small  quantity  of  wine  taken  fasting  caused  the  proportion 
of  carbonic  acid  in  the  expired  air  to  fall  immediately  from 
4  to  3  parts  per  100.  During  the  four  hours  following,  it 
oscillated  between  3*40,  3*10,  and  3.  The  administration  of 
a  second  dose,  followed  by  some  symptoms  of  intoxication, 
diminished  the  proportion  to  2*70  per  100.  Dr.  Fyfe,  of 
Edinburgh,  showed  that  the  depressing  .effects  of  an  alcoholic 
excess  were  continued  into  the  following  day.2  Dr.  Ham- 
mond, in  an  elaborate  and  excellent  paper  on  the  effects  of 
alcohol  and  tobacco  on  the  human  system,  observed  a  dimin- 
ished exhalation  of  carbonic  acid  following  the  ingestion  of 
twelve  drachms  of  alcohol  daily  for  five  days,  both  when  the 
system  was  kept  at  the  normal  standard  of  weight,  etc.,  by 
the  ingestion  of  the  habitual  quantity  of  food,  when  the 
weight  was  diminished  by  an  insufficient  diet,  and  when  the 
weight  was  increased  by  an  excessive  diet.3 

The  observations  of  Dr.  Smith,  which  were  all  made 
fasting,  show  a  certain  variation  in  the  effects  of  different  al- 
coholic beverages.  His  results  are  briefly  the  following : 

"  Brandy,  whiskey,  and  gin,  and  particularly  the  latter, 
almost  always  lessened  the  respiratory  changes  recorded, 
whilst  rum  as  commonly  increased  them.  Rum  and  milk 
had  a  very  pronounced  and  persistent  action,  and  there  was 
no  effect  on  the  sensorium.  Ale  and  porter  always  increased 
them,  whilst  sherry  wine  lessened  the  quantity  of  air  in- 
spired, but  slightly  increased  the  carbonic  acid  evolved. 

1  MILNE-EDWARDS,  Physiologic,  Paris,  1857,  tome  ii.,  p.  535. 

2  Ibid.    Prout  took  cognizance  only  of  the  proportion  of  carbonic  acid  in  the 
expired  air,  and  not  of  the  absolute  quantity  exhaled  in  a  given  time. 

s  WM.  A.  HAMMOND,  M.  D.,  The  Physiological  Effects  of  Alcohol  and  Tobacco 
upon  the  Human  System.  Physiological  Memoirs,  Philadelphia,  1863.  In  this 
valuable  paper  the  author  considers  the  general  influence  of  alcohol  and  tobacco 
on  nutrition,  as  indicated  by  the  production  of  urea,  carbonic  acid,  and  other  ex- 
crementitious  principles,  and  the  variations  in  the  weight  of  the  body. 


438  RESPIRATION. 

"  The  volatile  elements  of  alcohol,  gin,  rum,  sherry,  and 
port-wine,  when  inhaled,  lessened  the  quantity  of  carbonic 
acid  exhaled,  and  usually  lessened  the  quantity  of  air  inhaled. 
The  effect  of  fine  old  port-wine  was  very  decided  and  uni- 
form ;  and  it  is  known  that»wines  and  spirits  improve  in 
aroma  and  become  weaker  in  alcohol  by  age.  The  excito- 
respiratory  action  of  rum  is  probably  not  due  to  its  volatile 
elements." 1 

From  these  facts,  it  would  seem  that  the  most  constant 
effect  of  alcohol,  and  alcoholic  liquors,  such  as  wines  and 
spirits,  is  to  diminish  the  exhalation  of  carbonic  acid.  This 
effect  is  almost  instantaneous,  when  the  articles  are  taken 
into  the  stomach  fasting ;  and  when  taken  with  the  meals, 
the  increase  in  carbonic  acid  which  habitually  accompanies 
the  process  of  digestion  is  materially  lessened.  Rum,  which 
Dr.  Smith  found  to  be  a  respiratory  excitant,  is  an  exception 
to  this  rule.  Malt  liquors  seem  to  increase  the  exhalation  of 
carbonic  acid.  With  regard  to  alcohol  itself,  Dr.  Smith 
says :  "  The  action  of  pure  alcohol  was  much  more  to  increase 
than  to  lessen  the  respiratory  changes,  and  sometimes  the 
former  effect  was  well  pronounced."  a 

Regarding  as  one  of  the  great  sources  of  carbonic  acid 
the  development  of  this  principle  in  the  tissues,  whence  it  is 
taken  up  by  the  blood,  Dr.  Smith  attributes  the  grateful  and 
soothing  influence  of  tea,  coffee,  eau  sucree,  and  the  other 
beverages  which  he  classes  as  respiratory  excitants,  to  their 
action  in  facilitating  the  removal  of  this  principle  from  the 
system.  The  presence  of  carbonic  acid  in  the  tissues  and 
in  the  blood  produces  a  sense  of  malaise,  or  depression, 
which  we  should  suppose  would  be  relieved  by  any  thing 
which  facilitates  its  elimination.  It  is  undoubtedly  this  in- 
definite sense  of  discomfort  which  induces  the  act  of  sighing, 
by  which  the  air  in  the  lungs  is  more  effectually  renovated. 
This  view  is  sustained  by  the  fact  that  intellectual  fatigue 
and  mental  emotions  diminish  the  exhalation  of  carbonic  acid. 

1  Op.  cit.,  p.  731.  2  Loc.  tit. 


INFLUENCE    OF  MUSCULAR   ACTIVITY.  439 

Apjohn  cites  an  instance  in  which  the  proportion  of  carbonic 
acid  in  the  expirations  was  reduced  to  2*9  parts  per  100  under 
the  influence  of  mental  depression.1 

Dr.  Hammond  could  not  determine  any  modification  in  the 
exhalation  of  carbonic  acid  under  the  influence  of  tobacco.2 

Influence  of  Sleep. — All  who  have  directed  attention  to 
the  influence  of  sleep  upon  the  respiratory  products  have 
noted  a  marked  diminution  in  the  exhalation  of  carbonic 
acid ;  but  we  again  recur  to  the  experiments  of  Dr.  Smith 
for  exact  information  on  this  point.  Dr.  Smith  estimated 
the  quantity  of  carbonic  acid  exhaled  during  six  hours  of 
sleep,  at  night,  at  4,126  cubic  inches.  According  to  this 
observer,  the  quantity  during  the  night  is  to  the  quantity 
during  the  day,  in  complete  repose,  as  10  is  to  18.  During 
a  light  sleep,  the  exhalation  was  10*32,  and  during  profound 
sleep,  9'52  cubic  inches  per  minute. 

We  have  alluded  to  the  great  diminution  in  the  quantity 
of  oxygen  consumed  in  hibernating  animals,  while  in  a  torpid 
condition.  Regnault  and  Reiset  found  that  a  marmot  in 
hibernation  consumed  only  ^  of  the  oxygen  which  he  used 
in  his  active  condition.  In  the  same  animal  they  noted  an 
exhalation  of  carbonic  acid  equal  to  but  little  more  than  half 
the  weight  of  oxygen  absorbed ;  so  that  in  this  condition  the 
diminution  in  the  exhalation  of  carbonic  acid  is  proportion- 
ately even  greater  than  in  the  consumption  of  oxygen.3 

Influence  of  Muscular  Activity. — All  observers,  except 
Prout,4  agree  that  there  is  a  considerable  increase  in  the 


1  MILNE-EDWARDS,  Physiologic,  tome  ii.,  p.  535. 
a  Op.  cit. 


1  REGNAULT  ET  REISET,  Annales  de  Chimie  et  de  Physique,  3me  serie,  tome 
xxvi.,  p.  446.  The  marmot  consumed  in  five  days  13,088  grammes  of  oxygen, 
raid  exhaled  7,1Y4  grammes  of  carbonic  acid. 

4  Prout  only  noted  the  proportion  of  carbonic  acid  in  the  expired  air ;  and  as 
exercise  has  the  effect  of  immediately  and  largely  increasing  the  number  of  respi- 


440  RESPIRATION. 

exhalation  of  carbonic  acid  during  and  immediately  follow- 
ing muscular  exercise.  In  insects,  Mr.  Newport  has  found 
that  a  greater  quantity  is  sometimes  exhaled  in  an  hour  of 
violent  agitation,  than  in  twenty-four  hours  of  repose.  In  a 
drone,  the  exhalation  in  twentytfour  hours  was  O30  of  a  cubic 
inch,  and  during  violent  muscular  exertion  the  exhalation 
in  one  hour  was  O34:.1  Lavoisier  recognized  the  great  in- 
fluence of  muscular  activity  upon  the  respiratory  changes. 
In  treating  of  the  consumption  of  oxygen,  we  have  quoted 
his  observations  on  the  relative  quantities  of  air  vitiated  in 
repose  and  activity. 

Yierordt,  in  a  number  of  observations  on  the  human 
subject,  ascertained  that  moderate  exercise  increased  the 
average  quantity  of  air  respired  per  minute  by  nearly  nineteen 
cubic  inches,  and  that  there  was  an  increase  of  1*197  cubic 
inches  per  minute  in  the  absolute  quantity  of  carbonic  acid 
exhaled.2 

The  following  results  of  the  experiments  of  Dr.  Edward 
Smith  on  this  subject  are  very  definite  and  satisfactory  : 

In  walking  at  the  rate  of  two  miles  an  hour,  the  exhala- 
tion of  carbonic  acid  during  one  hour  was  equal  to  the  quan- 
tity produced  during  If  hour  of  repose,  with  food,  and  2J 
hours  of  repose,  without  food. 

"Walking  at  the  rate  of  three  miles  per  hour,  one  hour 
was  equal  to  2J  hours  with,  and  3  j-  hours  without  food. 

One  hour's  labor  at  the  tread-wheel,  while  actually  work- 
ing the  wheel,  was  equal  to  4^  hours  of  rest  with  food,  and  6 
hours  without  food.3 

The  various  observers  we  have  cited  have  remarked  that 


ratory  movements  and  the  quantity  of  air  passing  through  the  lungs,  and  as  we 
have  seen  the  quantity  of  carbonic  acid  in  the  expired  air  is  increased  in  propor- 
tion to  the  length  of  time  that  the  air  remains  in  the  lungs,  we  can  easily  see  the 
source  of  error  in  his  observations. 

*  MILNE-EDWARDS,  Physiologic,  tome  ii.,  p.  530. 

2  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iv.,  part  i.,  p.  348. 

'  Op.  cit.,  p.  713. 


INFLUENCE   OF  MOISTURE  AND  TEMPEKATUKE.  441 

when  muscular  exertion  is  carried  so  far  as  to  produce  great 
fatigue  and  exhaustion,  the  exhalation  of  carbonic  acid  is 
notably  diminished. 

Influence  of_  Moisture  and  Temperature. — Lehmann  has 
shown  that  the  exhalation  of  carbonic  acid  is  much  greater 
in  a  moist  than  in  a  dry  atmosphere.1  This  conclusion  was 
the  result  of  a  number  of  experiments  on  birds  and  animals 
confined  in  air  at  different  temperatures  and  different  degrees 
of  moisture.  He  found  that  35^-  oz.  av.  weight  of  rabbits,  at 
a  temperature  of  about  100°  Fahr.,  exhaled  during  an  hour 
before  noon,  in  a  dry  air,  about  15  cubic  inches  of  carbonic 
acid ;  while  in  a  moist  air,  at  the  same  temperature,  the  ex- 
halation was  about  22  cubic  inches. 

Disregarding  observations  on  the  influence  of  temperature 
in  cold-blooded  animals,  as  inapplicable  to  the  human  sub- 
ject, it  has  been  ascertained  that  the  exhalation  of  carbonic 
acid  is  much  greater  at  low  than  at  high  temperatures,  within 
the  limits  of  heat  and  cold  that  are  easily  borne  by  the  human 
subject ;  thus  following  the  rule  which  governs  the  consump- 
tion of  oxygen.  Crawford,  in  his  experiments  on  animal  heat, 
was  the  first  to  call  attention  to  this  fact.2  Since  then  it 
has  been  confirmed  by  numerous  observations  on  animals. 

The  experiments  of  Vierordt  on  the  human  subject  show 
that  there  is  an  increase  in  the  exhalation  of  carbonic  acid  of 
about  one-sixth,  under  the  influence  of  a  moderate  diminution 
in  temperature.  In  these  observations,  the  low  temperatures 
ranged  between  37*5°  and  59°,  and  the  high  temperatures  be- 
tween 60-5°  and  75*5°  Fahr.  He  found  the  quantity  of  air 
taken  into  the  lungs  slightly  increased  at  low  temperatures. 
The  absolute  quantity  of  carbonic  acid  exhaled  per  minute 
was  18*27  cubic  inches  for  the  low  temperatures,  and  15*73 
cubic  inches  for  the  high  temperatures.3 

1  LEHMANN,  Physiological  Chemistry,  Philadelphia,  1855,  vol.  ii.,  p.  444. 
3  MILNE-EDWARDS,  op.  cil.f  p.  548. 
3  Ibid.,  p.  551. 


442  RESPIRATION. 

Influence  of  the  /Season  of  the  Year. — It  has  been  pretty 
well  established  by  the  researches  of  Dr.  Smith,  that  spring 
is  the  season  of  the  greatest,  and  fall  the  season  of  the  least 
activity  of  the  respiratory  function. 

The  months  of  maximum  a*e :  January,  February,  March, 
and  April. 

The  months  of  minimum  are :  July,  August,  and  a  part 
of  September. 

The  months  of  decrease  are :  June  and  July. 

The  months  of  increase  are:  October,  November,  and 
December.1 

"W.  F.  Edwards,  in  1819,  showed  in  a  marked  manner 
this  influence  of  the  seasons  upon  the  respiratory  phenomena 
in  birds.  In  a  series  of  very  curious  observations,  which  he 
repeatedly  verified,  it  was  demonstrated  that  the  increase  in 
the  activity  of  respiration  during  the  winter  was  to  a  certain 
extent  independent  of  the  immediate  influence  of  the  sur- 
rounding temperature.  In  the  month  of  January  he  confined 
six  yellow-hammers  in  a  receiver  containing  71*4  cubic  inches 
of  air,  carrying  the  temperature  to  from  69°  to  70°  Fahr. 
The  mean  duration  of  their  life  was  62  minutes  25  seconds. 
In  the  months  of  August  and  September  he  repeated  the  ex- 
periment on  thirteen  birds  of  the  same  species,  at  the  same 
temperature.  The  mean  duration  of  life  was  82  minutes.3 

These  experiments  have  an  important  bearing  on  our 
views  concerning  the  essential  nature  of  the  respiratory  func- 
tion. They  seem  to  indicate  that  the  respiratory  processes 
are  intimately  connected  with  nutrition.  Like  the  other  nu- 
tritive phenomena,  they  undoubtedly  vary  at  different  sea- 
sons of  the  year,  and  are  to  a  certain  extent  independent  of 
sudden  and  transitory  conditions.  During  the  winter,  more 
air  is  habitually  used  than  in  summer,  and  the  respiratory 

1  Resume  de  Recherches  Experimental^  sur  la  Respiration. — Journal  de  la 
Physiologic,  1860,  tome  iii.,  p.  519. 

a  W.  F.  EDWARDS,  De  V Influence  des  Agens  Physiques  sur  la  Vie,  Paris,  1824, 
p,  200. 


RELATIONS  BETWEEN  OXYGEN  AND  CARBONIC  ACID.   443 

processes  cannot  be  immediately  brought  down  to  the  sum- 
mer standard  by  a  mere  elevation  of  temperature. 

Observations  on  the  influence  of  barometric  pressure  are 
not  sufficiently  definite  in  their  results  to  warrant  any  exact 
conclusions. 

Some  physiologists  have  attempted  to  fix  certain  hours  of 
the  day  when  the  exhalation  of  carbonic  acid  is  at  its  maxi- 
mum, or  at  its  minimum ;  but  the  respiratory  activity  is  in- 
fluenced by  such  a  variety  of  conditions,  that  it  is  impossible 
to  do  this  with  any  degree  of  accuracy. 

Relations  between  the  Quantity  of  Oxygen  consumed  and  the 
Quantity  of  Carbonic  Acid  exhaled. 

Oxygen  unites  with  carbon  in  certain  proportions,  to  form 
carbonic  acid  gas,  the  volume  of  which  is  precisely  equal  to 
the  volume  of  the  oxygen  which  enters  into  its  composition. 
In  studying  the  relations  of  the  volumes  of  these  gases  in 
respiration,  we  have  a  guide  in  the  comparison  of  the  volumes 
of  the  inspired  and  expired  air.  It  is  now  generally  recog- 
nized that  the  volume  of  air  expired  is  less,  at  an  equal  tem- 
perature, than  the  volume  of  air  inspired.  Assuming,  then, 
that  the  changes  in  the  expired  air,  as  regards  nitrogen,  and 
all  gases  except  oxygen  or  carbonic  acid,  are  insignificant,  it 
must  be  admitted  that  a  certain  quantity  of  the  oxygen  con- 
sumed by  the  economy  is  unaccounted  for  by  the  oxygen 
which  enters  into  the  composition  of  the  carbonic  acid  ex- 
haled. "We  have  already  noted  that  from  -fa  to  -fa,  or  about 
1'4:  to  2  per  cent,  of  the  inspired  air  is  lost  in  the  lungs ; '  or 
it  may  be  stated,  in  general  terms,  that  the  oxygen  absorbed 
is  equal  to  about  five  per  cent,  of  the  volume  of  air  inspired, 
and  the  carbonic  acid  exhaled  only  about  four  per  cent.  A 
certain  amount  of  the  deficiency  in  volume  of  the  expired  air 
is  then  to  be  accounted  for  by  a  deficiency  in  the  exhalation 
of  carbonic  acid. 

1  Vide  page  405. 


RESPIRATION. 

The  experiments  of  Kegnault  and  Eeiset,  to  which  fre- 
quent reference  has  been  made,  have  a  most  important  bear- 
ing on  the  question  under  consideration.  As  these  observers 
were  able  to  carefully  measure  the  entire  quantities  of  oxygen 
consumed  and  carbonic  acid  produced  in  a  given  time,  the 
relation  between  the  two  gases  was  kept  constantly  in  view. 
They  found  great  variations  in  this  relation,  mainly  dependent 
upon  the  regimen  of  the  animal.  The  total  loss  of  oxygen 
was  found  to  be  much  greater  in  carnivorous  than  in  herbiv- 
orous animals ;  and  in  animals  that  could  be  subjected  to  a 
mixed  diet,  by  regulating  the  food,  this  was  made  to  vary  be- 
tween the  two  extremes.  The  mean  of  seven  experiments  on 
dogs  showed  that  for  every  1,000  parts  of  oxygen  consumed, 
Y45  parts  were  exhaled  in  the  form  of  carbonic  acid.  In  six 
experiments  on  rabbits,  the  mean  was  919  for  every  1,000 
parts  of  oxygen.1 

In  animals  fed  on  grains,  the  proportion  of  carbonic  acid 
exhaled  was  greatest,  sometimes  passing  a  little  beyond  the 
volume  of  oxygen  consumed. 

"  The  relation  is  nearly  constant  for  animals  of  the  same 
species  which  are  subjected  to  a  perfectly  uniform  alimenta- 
tion, as  is  easy  to  realize  as  regards  dogs  ;  but  it  varies  not- 
ably in  animals  of  the  same  species,  and  in  the  same  animal, 
submitted  to  the  same  .regimen,  but  in  which  we  cannot  reg- 
ulate the  alimentation,  as  in  fowls." 2 

When  herbivorous  animals  were  entirely  deprived  of  food, 
the  relation  between  the  gases  was  the  same  as  in  carnivorous 
animals. 

The  final  result  of  the  experiments  of  Eegnault  and 
Reiset  was,  that  the  "  relation  between  the  oxygen  contained 
in  the  carbonic  acid  and  the  total  oxygen  consumed,  varies, 
in  the  same  animal,  from  0'62  to  1*04,  according  to  the  regi- 
men to  which  he  is  subjected." 

1  REGXAuti  and  REISET,  Recherches  Chimiques  sur  la  Respiration, — Annafai 
de  Chimie  et  de  Physique,  3me  serie,  tome  xxvi. 

2  Ibid.,  p.  514. 


SOUECES   OF   CARBONIC   ACID   EXHALED.  445 

These  observations  on  animals  have  been  confirmed  in 
the  human  subject  by  M.  Doyere,  who  found  a  great  varia- 
tion in  the  relations  of  the  two  gases  in  respiration ;  the  vol- 
ume of  carbonic  acid  exhaled  varying  between  1-087  and 
O862  for  1  part  of  oxygen  consumed.1 

The  destination  of  the  oxygen  which  is  not  represented 
in  the  carbonic  acid  exhaled  is  obscure.  Some  have  thought 
that  it  unites  with  hydrogen  to  form  water ;  but  there 
is  not  sufficient  evidence  of  the  formation  of  water  in  the 
economy,  for  researches  have  failed  to  show  that  there  is 
more  thrown  off  from  the  body  than  is  taken  in  with  food 
and  drink. 

The  variations  in  the  relative  volumes  of  oxygen  con- 
sumed and  carbonic  acid  produced  in  respiration  are  not 
favorable  to  the  hypothesis  that  the  carbonic  acid  is  the  re- 
sult of  a  direct  action  of  oxygen  upon  carbonaceous  matters. 
We  should  hardly  expect  a  definite  relation  to  exist  between 
these  two  gases  in  respiration,  when  we  find  carbonic  acid 
exhaled  in  the  absence  of  oxygen,  as  has  been  shown  by  the 
experiments  of  "W.  F.  Edwards  and  Geo.  Liebig. 

Sources  of  Carbonic  Acid  in  the  Expired  Air. — All  the 
carbonic  acid  in  the  expired  air  comes  from  the  venous  blood, 
where  it  exists  in  two  forms :  in  a  free  state  in  simple  solution, 
or  at  least  in  a  state  of  very  feeble  combination,  and  in  union 
with  bases,  forming  the  carbonates  and  bicarbonates.  That 
which  exists  in  solution  in  the  blood  is  simply  displaced  by 
the  oxygen  of  the  air  and  exhaled.  The  alkaline  carbonates 
and  bicarbonates  of  the  blood,  coming  to  the  lungs,  meet 
with  pneumic  acid  (discovered  by  Yerdeil  in  1851),  and  are 
decomposed,  giving  rise  to  a  further  evolution  of  gas.  It  is 
pneumic  acid  which  gives  the  constant  acid  reaction  to  the 
tissue  of  the  lungs.  This  principle  is  found  in  the  pulmo- 
nary parenchyma  at  all  periods  of  life,  from  which  it  may 
be  extracted  by  the  proper  manipulations,  and  obtained 

1  MILNE-EDWARDS,  Physiologie,  tome  ii.,  p.  694. 


446  RESPIRATION. 

in  a  crystalline  form.  Its  quantity  is  not  very  great.  The 
lungs  of  a  female  who  suffered  death  by  decapitation  con- 
tained about  0-77  of  a  grain.1 

The  action  of  pneumic  acid  upon  the  bicarbonates  in  the 
blood  is  exemplified  in  a  marked  manner  by  certain  experi- 
ments of  Bernard.  When  bicarbonate  of  soda  is  injected 
into  the  jugular  of  a  living  animal,  a  rabbit,  for  example,  it 
is  decomposed  as  fast  as  it  gets  to  the  lungs,  and  carbonic 
acid  is  evolved.  This  experiment  produces  no  inconvenience 
to  the  animal  when  the  bicarbonate  is  introduced  slowly ;  but 
when  it  is  injected  in  too  great  quantity,  the  evolution 
of  gas  in  the  lungs  is  so  great  as  to  fill  the  pulmonary  struc- 
ture and  even  the  heart  and  great  vessels,  and  death  is  the 
result.3 

Exhalation  of  Watery  Vapor. — The  fact  that  the  expired 
air  contains  a  considerable  quantity  of  watery  vapor  has  long 
been  recognized ;  and  most  of  the  earlier  experimenters  who 
directed  their  attention  to  the  phenomena  of  respiration 
made  the  estimation  of  the  quantity  exhaled,  and  the  laws 
which  regulate  pulmonary  transpiration,  the  subject  of  in- 
vestigation. It  is  evident  that  there  must  be  many  cir- 
cumstances materially  influencing  this  process,  such  as  the 
hygrometric  condition  of  the  atmosphere,  temperature,  ex- 
tent of  respiratory  surface,  etc.,  which  are  of  sufficient  impor- 
tance to  demand  special  consideration.  In  many  points  of 
view,  also,  it  is  interesting  to  know  the  absolute  quantity  of 
exhalation  from  the  lungs. 

1  ROBIN  and  VERDEIL,  Chimie  Anatomique  et  Physiologique,  Paris,  1853,  tome 
ii.,  p.  460. 

2  Op.  tit.,  tome  i.,  p.  165.     These  experiments  referred  to  the  decomposition  of 
cyanide  of  potassium  in  the  lungs,  as  well  as  bicarbonate  of  soda.     They  were 
published  in  the  Archives  Generates  in  1848,  before  the  discovery  of  pneumic 
acid,  and  Bernard  expressed  surprise  that  the  two  substances  experimented  upon, 
which  required  an  acid  for  their  decomposition,  should  be  decomposed  in  an  al- 
kaline fluid  like  the  blood.    Though  made  without  a  knowledge  of  the  existence 
of  pneumic  acid,  the  observations  none  the  less  illustrated  its  physiological 
action. 


EXHALATION  OF  WATERY  VAPOK.  447 

When  the  surrounding  atmosphere  has  a  temperature  below 
40°  or  43°  Fahr.,  a  distinct  cloud  is  produced  by  the  condensa- 
tion of  the  vapor  of  the  breath.  By  breathing  upon  any 
polished  surface,  it  is  momentarily  tarnished  by  the  condensed 
moisture.  Though  the  fact  that  watery  vapor  is  contained  in 
the  breath  is  thus  easily  demonstrated,  the  estimation  of  its 
absolute  quantity  presents  difficulties  which  were  not  overcome 
by  the  older  physiologists.  Hales  collected  the  vapor  of  the 
breath  by  expiring  through  wood  ashes,1  which  was  the  first 
attempt  to  estimate  the  amount  of  this  exhalation  by  absorp- 
tion. With  the  present  improved  methods  of  analysis  there 
are  many  very  accurate  means  of  estimating  watery  vapor. 
One  method  is  by  the  use  of  Liebig's  bulbs  filled  with  sul- 
phuric acid,  or  tubes  filled  with  chloride  of  calcium,  both  of 
which  articles  have  a  great  avidity  for  water.  From  a  large 
number  of  observations  on  his  own  person  and  eight  others, 
collecting  the  water  by  sulphuric  acid,  Yalentin  makes  the 
following  estimate  of  the  weight  of  water  exhaled  from  the 
lungs  in  twenty-four  hours : 

In  his  own  person,  the  exhalation  in  24  hours  was  6,055 
grains. 

In  a  young  man  of  small  size,  the  quantity  was  5,042 
grains. 

In  a  student  rather  above  the  ordinary  height,  the  quan- 
tity was  11,930  grains. 

The  mean  of  his  observations  gave  a  daily  exhalation  of 
8,333  grains,  or  about  1 J-  Ib.  av.2 

1  HALES,  Statical  Essays,  London,  1739,  vol.  ii.,  p.  326.      Sanctorius,   in 
1614,  was  the  first  (MILNE-EDWARDS,  Physiologic,  vol.  ii.,  p.  602)  to  attempt  the 
estimation  of  the  exhalation  of  vapor  of  water  from  the  body  by  comparing  the 
gam.  in  weight  due  to  the  ingestion  of  aliments  with  the  loss  by  transpiration. 
We  pass  over  the  estimates  of  Lavoisier  and  Seguin,  Keill,  Abernethy,  and 
others,  and  give  only  the  more  exact  results  obtained  by  Valentin.     Dalton, 
estimating  the  quantity  of  air  passing  through  the  lungs  in  respiration,  and  as- 
suming that  it  passes  out  of  the  lungs  saturated  with  watery  vapor,  makes  an  es- 
timate of  the  total  exhalation  in  the  twenty-four  hours,  which  corresponds  pretty 
closely  with  the  results  obtained  by  Valentin. 

2  MILNE-EDWARDS,  op.  cit.,  p.  621. 


448  RESPIRATION. 

The  extent  of  respiratory  surface  has  a  very  marked  in- 
fluence on  the  quantity  of  watery  vapor  exhaled.  This  fact 
is  very  well  shown  by  a  comparison  of  the  exhalation  in  the 
adult  and  in  old  age,  when  the  extent  of  respiratory  surface 
is  much  diminished.  Barral  found  the  exhalation  in  an  old 
man  less  than  half  that  of  the  adult.1 

It  is  evident  that  the  absolute  quantity  of  vapor  exhaled 
is  increased  when  respiration  is  accelerated. 

The  quantity  of  water  in  the  blood  also  exerts  an  impor- 
tant influence.  Yalentin  found  that  the  pulmonary  transpira- 
tion was  more  than  doubled  in  a  man  immediately  after  drink- 
ing a  large  quantity  of  water.1 

The  vapor  in  the  expired  air  is  derived  from  the  entire 
surface  which  is  traversed  in  respiration,  and  not  exclusively 
from  the  air-cells.  The  air  which  passes  into  the  lungs  de- 
rives a  certain  amount  of  moisture  from  the  mouth,  nares, 
and  trachea.  The  great  vascularity  of  the  mucous  membranes 
in  these  situations,  as  well  as  of  the  air-cells,  and  the  great 
number  of  mucous  glands  which  they  contain,  serve  to  keep 
the  respiratory  surfaces  continually  moist.  This  is  important, 
for  only  moist  membranes  allow  the  free  passage  of  gases, 
which  is  of  course  essential  to  the  process  of  respiration. 

Exhalation  of  Ammonia. — The  most  recent  and  extended 
observations  on  the  exhalation  of  ammonia  by  the  lungs,  are 
those  of  Dr.  Richardson,  to  which  we  have  already  alluded 
in  treating  of  the  coagulation  of  the  blood.  In  more  than  a 
thousand  experiments,  made  upon  persons  of  both  sexes,  and 
on  various  of  the  inferior  animals,  with  but  one  exception,  a 
notable  quantity  of  ammonia  was  found  in  the  expired  air. 
Dr.  Richardson  found  the  quantity  very  variable  at  different 
times  of  the  day.  At  certain  periods  it  is  absent. 

1  MILNE-EDWARDS,  op.  cit.,  p.  625,  note. 

8  Ibid.,  p.  607,  note.    It  has  not  been  thought  necessary  to  discuss  the  in 
fiuences  of  dry  and  moist  atmosphere,  barometric  pressure,  and  temperature, 
ich  are    urel      hsical  in  their  character. 


iiueuues  01  ury  auu  moist  aimospnere,    uai 
which  are  purely  physical  in  their  character. 


EXHALATION.  OF   ORGANIC  MATTER.  449 

In  a  number  of  observations  made  on  his  own  person,  the 
following  variations  were  noted  : 1 

On  rising  in  the  morning,  after  a  sound  night's  rest,  the 
breath  contained  no  ammonia. 

In  the  evening,  when  fatigued  and  exhausted,  and  after 
exercise,  the  exhalation  was  generally  considerable. 

During  a  high  temperature  the  exhalation  is  considerable, 
especially  after  exercise;  but  during  cold  weather  the  exha- 
lation is  very  slight,  or  it  may  be  absent  altogether. 

The  amount  of  ammonia  exhaled  is  greatest  at  the  end 
of  an  expiration:  If  short  and  rapid  expirations  be  made, 
the  exhalation  ceases  until  the  respirations  become  deeper 
and  more  prolonged. 

Ammonia  has  long  been  recognized  as  an  exhalation  from 
the  human  body  in  health,  from  the  skin  as  well  as  the  lungs. 
Dr.  Richardson  calls  attention  in  his  essay  to  the  observa- 
tions of  Mr.  Reade,  Dr.  Reuling,  Yiale  and  Latini,  and 
others  on  this  subject.  Reuling  has  shown  that  the  quantity 
of  ammonia  in  the  expired  air  is  increased  in  certain  diseases, 
particularly  in  uremia.2  Its  characters  in  the  expired  air 
are  frequently  so  marked,  that  patients  who  are  entirely 
unacquainted  with  the  pathology  of  uremia  sometimes 
recognize  an  ammoniacal  odor  in  their  own  breath. 

Exhalation  of  Organic  Matter,  etc. — The  pulmonary  sur- 
face exhales  a  small  quantity  of  organic  matter.  This  has 
never  been  collected  in  sufficient  quantity  to  enable  us  to 
recognize  in  it  any  peculiar  or  distinctive  properties,  but  its 
presence  may  be  demonstrated  by  the  fact  that  a  sponge 
completely  saturated  with  the  exhalations  from  the  lungs,  or 
the  vapor  from  the  lungs  condensed  in  a  glass  vessel,  will 
undergo  putrefaction,  a  property  distinctive  of  organic  sub- 
stances. 

It  is  well  known  that  certain  substances  which  are  only 

1  The  Cause  of  the  Coagulation  of  the  Blood,  London,  1857,  p.  360  et  seq. 
a  In  LEHMANN'S  Physiological  Chemistry,  Philadelphia,  1855,  vol.  ii.,  p.  434. 
29 


450  RESPIRATION. 

occasionally  found  in  the  blood  may  be  eliminated  by  the 
lungs.  Alcohol  is  partly  removed  from  the  system  in  this 
way;  and  its  presence,  with  certain  odorous  principles,  in 
the  breath  is  pretty  constant  in  those  who  take  liquors  ha- 
bitually in  considerable  quantity.  The  odor  of  garlics,  onions, 
turpentine,  and  many  other  principles  which  are  taken  into 
the  stomach,  may  be  recognized  in  the  expired  air.  The 
lungs  are  among  the  important  organs  for  the  elimination  of 
foreign  matters  from  the  system. 

The  action  of  the  lungs  in  the  elimination  of  certain  gases, 
which  are  poisonous  in  very  small  quantities  when  they  are 
absorbed  in  the  lungs  and  carried  to  the  general  system  in 
the  arterial  blood,  is  very  well  shown  by  the  experiments  of 
Bernard.  Sulphuretted  hydrogen,  which  produces  death  in 
a  bird  when  it  exists  in  the  atmosphere  in  the  proportion  of 
1  to  800,  may  be  taken  into  the  stomach  in  solution  with 
impunity,  and  even  be  injected  into  the  venous  system ;  in 
both  instances  being  eliminated  by  the  lungs  with  great 
promptness  and  rapidity.1  Nysten  showed  that  the  carbonic 
oxide,  one  of  the  most  violent  and  rapid  in  its  effects  of  any 
of  the  poisonous  gases  when  inhaled,  could  be  injected  into 
the  veins  with  impunity,  by  simply  taking  care  to  introduce 
it  only  as  rapidly  as  it  is  absorbed  by  the  blood.2 

The  lungs,  then,  while  they  present  an  immense  and  rap- 
idly absorbing  surface  for  volatile  poisonous  substances,  are 
capable  of  relieving  the  system  of  some  of  these  substances 
by  exhalation,  when  they  find  their  way  into  the  veins. 

1  BERNARD,  Lemons  sur  les  Effets  des  Substances  Toxiques  et  Medicamenteuses, 
Paris,  1857,  p.  58.     In  an  experiment  on  a  dog  of  medium  size,  injecting  a  little 
more  than  a  fluid  drachm  of  water  saturated  with  sulphuretted  hydrogen  into  the 
jugular  vein,  the  gas  was  detected  almost  instantly  in  the  expired  air,  and  the 
animal  suffered  no  inconvenience  from  the  operation.     The  gas  appeared  in  the 
breath  in  sixty-five  seconds,  when  about  an  ounce  of  the  solution  was  injected 
into  the  rectum.     We  have  repeatedly  verified  the  experiment  of  Bernard  showing 
the  almost  instantaneous  elimination  of  this  gas  by  the  lungs,  when  injected  into 
the  veins. 

2  NYSTEN,  Recherches  de  Physiologic,  etc.,  Paris,  1811,  p.  81  et  seq. 


EXHALATION   OF  NITEOGEN.  451 

Exhalation  of  Nitrogen. — The  latest  and  most  accurate 
direct  experiments,  particularly  those  of  Regnault  and  Reiset, 
show  that  the  exhalation  of  a  small  quantity  of  nitrogen  is  a 
pretty  constant  respiratory  phenomenon.  From  a  large  num- 
ber of  experiments  on  dogs,  rabbits,  fowls,  and  birds,  these  ob- 
servers came  to  the  conclusion  that  when  animals  are  subject- 
ed to  their  habitual  regimen,  they  exhale  a  quantity  of  nitrogen 
equal  in  weight  to  from  -^-$  to  TV  of.  the  weight  of  oxygen 
consumed.  In  birds,  during  inanition,  they  sometimes  observ 
ed  an  absorption  of  nitrogen,  but  this  was  rarely  seen  in  mam 
mals.1  Boussingault,  by  the  indirect  method,  estimating  the 
nitrogen  taken  into  the  body  and  comparing  it  with  the  en- 
tire quantity  discharged,  arrived  at  the  same  results  in  ex- 
periments upon  a  cow.2  Barral,  by  the  same  method,  con- 
firmed these  observations  by  experiments  on  the  human 
subject.3 

In  spite  of  the  conflicting  testimony  of  the  older  physi- 
ologists, there  can  now  be  no  doubt  that,  under  ordinary 
physiological  conditions,  there  is  an  exhalation  by  the  lungs 
of  a  small  quantity  of  nitrogen. 

1  REGNAULT  and  REISET,  op.  cit.,  Annales  de  Chimie  et  de  Physique,  3me 
serie,  tome  xxvi.,  pp.  510,  511. 

8  BOUSSINGAULT,  Memoires  de  Chimie  Agricole  et  de  Physiologic,  Paris,  1854, 
pp.  1-24. 

3  LONGET,  Physiologic,  Paris,  1861,  tome  i.,  p.  543. 


CHAPTEE  XIII. 


CHANGES   OF   THE   BLOOD   IN   KESPERATION. 


Difference  in  color  between  arterial  and  venous  blood  —  Comparison  of  the  gases 
in  venous  and  arterial  blood  —  Observations  of  Magnus  —  Analysis  of  the  blood 
for  gases  —  Kelative  quantities  of  oxygen  and  carbonic  acid  in  venous  and  ar- 
terial blood  —  Nitrogen  of  the  blood  —  Condition  of  the  gases  in  the  blood  — 
Mechanism  of  the  interchange  of  gases  between  the  blood  and  the  air  in  the 
lungs  —  General  differences  in  the  composition  of  arterial  and  venous  blood. 

IT  is  to  be  expected  that  the  blood,  receiving  on  the  one 
hand  all  the  products  of  digestion,  and  on  the  other  the 
products  of  destructive  assimilation  or  decay  of  the  tissues, 
connected  with  the  lymphatic  system,  and  exposed  to  the 
action  of  the  air  in  the  lungs,  should  present  important  dif- 
ferences in  composition  in  different  parts  of  the  vascular 
system. 

In  the  first  place,  there  is  a  marked  difference  in  color, 
composition,  and  properties,  between  the  blood  in  the  arte- 
ries and  in  the  veins;  the  change  from  venous  to  arterial 
blood  being  effected  almost  instantaneously  in  its  passage 
through  the  lungs.  The  blood  which  goes  to  the  lungs  is  a 
mixture  of  the  fluid  collected  from  all  parts  of  the  body; 
and  we  have  seen  that  it  presents  great  differences  in  its 
composition  in  different  parts  of  the  venous  system.  In 
some  veins  it  is  almost  black,  and  in  some  nearly  as  red  as  in 
the  arteries.  In  the  hepatic  vein  it  contains  sugar,  and  its 
fibrin,  albumen,  and  corpuscles  are  diminished  ;  in  the  portal 


CHANGES   OF  THE  BLOOD  EST  RESPIRATION.  453 

vein,  during  digestion,  it  contains  materials  absorbed  from 
the  alimentary  canal ;  and  finally,  there  is  every  reason  to 
suppose  that  parts  which  require  different  materials  for  their 
nutrition,  and  produce  different  excrementitious  principles, 
exert  different  influences  on  the  constitution  of  the  blood 
which  passes  through  them.  After  this  mixture  of  different 
kinds  of  blood  has  been  collected  in  the  right  side  of  the 
heart  and  passed  through  the  lungs,  it  is  returned  to  the  left 
side,  and  sent  to  the  system,  thoroughly  changed  and  reno- 
vated, and,  as  arterial  blood,  has  a  uniform  composition,  as 
far  as  can  be  ascertained,  in  all  parts  of  the  system.  This 
fact  has  been  proven  by  the  direct  experiments  of  Beclard, 
who  analyzed  blood  from  the  abdominal  aorta,  the  carotid, 
temporal,  occipital,  crural,  and  epigastric  arteries,  in  the 
same  animal  during  life,  and  found  the  composition  identical 
in  all  the  specimens.  His  experiments  were  performed  on 
horses  and  dogs,  and  care  was  taken  to  draw  but  a  small 
quantity  from  each  vessel,  so  as  not  to  change  the  constitu- 
tion of  the  fluid.1  The  change,  therefore,  which  the  blood 
undergoes  in  its  passage  through  the  lungs,  is  the  transfor- 
mation of  the  mixture  of  venous  blood  from  all  parts  of  the 
organism  into  a  fluid  of  uniform  character,  which  is  capable 
of  nourishing  and  sustaining  the  function  of  every  tissue  and 
organ  of  the  body. 

The  capital  phenomena  of  respiration,  as  regards  the  air 
in  the  lungs,  are  loss  of  oxygen  and  gain  of  carbonic  acid ; 
the  other  phenomena  being  accessory  and  comparatively  un- 
important. As  the  blood  is  capable  of  holding  gases  in  solu- 
tion, in  studying  the  essential  changes  which  this  fluid  un- 
dergoes in  respiration,  we  look  for  them  in  connection  with 
the  proportions  of  oxygen  and  carbonic  acid  before  and  after 
it  has  passed  through  the  lungs.  In  respiration,  the  most 
marked  effect  on  the  venous  blood  is  change  in  color. 

1  Archives  Generales  de  Medecine,  4me  serie,  tome  sviii.,  p.  123 ;  and  BEBARD, 
Physiologic,  tome  iii.,  p.  369. 


454:  KESPIEATION. 

Difference  in  Color  between  Arterial  and  Venous  JSlood. 
— We  have  already  considered  this  in  treating  of  the  proper- 
ties of  the  blood,  and  will  only  take  up  in  this  connection  the 
cause  of  the  remarkable  change  in  the  color  of  the  blood 
in  the  lungs.  This  change  «s  instantaneous,  and,  long  be- 
fore the  discovery  of  oxygen  by  Priestley,  was  recognized 
by  Lower,  Goodwyn,  and  others,  as  due  to  the  action  of 
the  air. 

The  celebrated  experiment  of  Bichat  showed  the  effect 
on  the  color  of  the  blood  in  the  arteries,  of  preventing  the 
access  of  fresh  air  to  the  lungs.  This  observer  adapted  a 
stop-cock  to  the  trachea  of  a  dog,  by  which  he  could  regu- 
late the  entrance  of  air  into  the  lungs,  and  exposing  the  caro- 
tid artery,  adapted  a  small  one  to  this  vessel.  "When  he  pre- 
vented the  air  from  getting  to  the  lungs  by  closing  the 
stop-cock  in  the  trachea,  the  blood  became  black  in  the 
artery,  but  regained  its  florid  hue  when  air  was  readmitted 
to  the  lungs.1 

The  influence  of  air  in  changing  the  color  of  venous  blood 
may  be  noted  in  blood  which  has  been  drawn  from  the  body ; 
as  is  exemplified  by  the  red  color  of  that  portion  of  a  clot, 
or  the  surface  of  defibrinated  venous  blood,  which  is  exposed 
to  the  air.  If  we  cut  into  a  clot  of  venous  blood,  the  interior 
is  almost  black,  but  becomes  red  on  exposure  to  the  air  for  a 
very  few  seconds. 

We  have  been  in  the  habit  of  illustrating  the  physiologi- 
cal influence  of  the  air  on  venous  blood  by  the  following 
simple  experiment :  Removing  the  lungs  of  an  animal  (a 
dog)  just  killed,  the  nozzle  of  a  syringe  is  secured  in  the  pul- 
monary artery  by  a  ligature,  and  a  canula,  connected  with  a 
rubber  tube  which  empties  into  a  glass  vessel,  is  secured  in 
the  pulmonary  vein.  Adapting  a  bellows  to  the  trachea,  we 
imitate  the  process  of  respiration ;  and  if  defibrinated  venous 
blood  be  carefully  injected  through  the  lungs,  it  will  be  return- 

1  XAY.  BICHAT,  Recherches  Physiologiques  sur  la  Vie  et  la  Mart,  5 me  Edition, 
par  F.  MAGENDIE,  Paris,  1829,  p.  386. 


CHANGE  IN  COLOR  OF  THE  BLOOD.          455 

ed  by  the  pulmonary  vein  with  the  bright  red  color  of  arterial 
blood.  When  the  artificial  respiration  is  interrupted,  the 
blood  passes  through  the  lungs  without  change.1  In  expos- 
ing the  thoracic  organs,  and  keeping  up  artificial  respiration, 
repeating  the  celebrated  experiment  of  Robert  Hook,  made 
before  the  Royal  Society  in  1664,  we  can  see  through  the 
thin  walls  of  the  auricles  the  red  color  of  the  blood  on  the 
left  side  contrasting  with  the  dark  venous  blood  on  the  right. 

Since  the  discovery  of  oxygen,  it  has  been  ascertained 
that  this  is  the  only  constituent  of  the  air  which  is  capable 
of  arterializing  the  blood.  Priestley  showed  that  venous 
blood  is  not  changed  in  color  by  nitrogen,  hydrogen,  or  car- 
bonic acid  ;  while  all  these  gases,  by  displacing  oxygen,  will 
change  the  arterial  blood  from  red  to  black.2 

The  elements  of  the  blood  which  absorb  the  greater  part 
of  the  oxygen  are  the  red  corpuscles.  While  the  plasma  will 
absorb,  perhaps,  twice  as  much  gas  as  pure  water,  it  has  been 
shown  by  Magnus  and  Gay-Lussac  that  the  corpuscles  will 
absorb  from  ten  to  thirteen  times  as  much.3  By  some  the 
proportion  is  put  much  higher.  The  red  corpuscles  may  be 
considered  as  the  respiratory  elements  of  the  blood.  It  is 

1  This  demonstration  is  very  striking,  especially  if  we  use  a  syringe  with  a 
double  nozzle,  one  point  secured  in  the  pulmonary  artery,  and  the  other  simply 
carrying  the  blood  by  a  rubber  tube  into  a  glass  vessel.  Receiving  the  blood 
which  passes  through  the  lungs,  and  that  which  simply  passes  through  the  tube, 
into  two  tall  glass  vessels,  the  one  is  of  a  bright  red,  and  the  other  retains  its 
dark  color.  In  preparing  for  the  experiment  it  is  necessary,  immediately  after 
removing  the  lungs  from  the  animal,  to  inject  them  with  a  little  defibrinated  blood, 
so  as  to  remove  the  coagulating  blood  from  the  pulmonary  capillaries,  which  would 
otherwise  become  obstructed.  The  injection  should  be  made  gently  and  gradually, 
to  avoid  extravasation.  Defibrinated  ox-blood  may  be  used.  The  most  conven- 
ient way  to  secure  the  canula3  in  the  vessels  is  to  push  them  into  the  pulmonary 
artery  through  the  right  ventricle,  and  into  the  pulmonary  vein  through  the  left 
auricle. 

3  Carbonic  oxide  and  nitrous  oxide  have  a  strong  affinity  for  the  blood-corpus- 
cles, and  become  fixed  in  them,  the  former  giving  the  blood  a  vivid  red  color. 
Sugar  and  many  salts  will  also  redden  venous  blood.  These  agents,  however,  do 
not  impart  the  physiological  properties  of  arterial  blood. 

9  ROBIN  and  VERDEIL,  op.  cit.,  tome  i.,  p.  32. 


456  RESPIRATION. 

undoubtedly  true  that  the  corpuscles,  deprived  of  their  natu- 
ral plasma,  are  not  changed  in  color  by  being  exposed  to  the 
air,  or  even  to  pure  oxygen.  Dr.  Stevens,  after  removing 
the  serum  from  a  clot  by  repeated  washings  with  pure  water, 
found  that  the  color  remained  J)lack  when  exposed  to  the  air,1 
but  was  reddened  by  the  addition  of  its  serum,  or  certain 
saline  solutions.  From  this  he  reasoned  that  the  red  color  of 
arterial  blood  is  due  to  the  saline  constituents  of  the  plasma. 
This  is  true ;  but  the  saline  constituents  of  the  plasma  affect 
the  color  indirectly,  by  maintaining  the  anatomical  integrity 
of  the  corpuscles.  If  blood  be  received  from  a  vein  into  pure 
water,  it  remains  almost  black,  however  long  it  may  be  ex- 
posed to  the  air,2  from  the  fact  that  the  corpuscles  are  de- 
stroyed. These  facts  are  only  additional  evidence  of  the 
function  of  the  red  corpuscles  in  absorbing  oxygen  and  car- 
rying it  to  the  tissues.  According  to  the  late  researches 
of  Fernet,  which  have  been  confirmed  by  L.  Meyer,  the  vol- 
ume of  oxygen  fixed  by  the  corpuscles  is  about  twenty-five 
times  that  which  is  dissolved  in  the  plasma.3 

Comparison  of  the  Gases  in  Venous  and  Arterial  Blood. — 
The  demonstration  of  the  fact  that  free  oxygen  and  carbonic 
acid  exist  in  the  blood,  with  a  knowledge  of  the  relative  pro- 
portion of  these  gases  in  the  blood  before  and  after  its  pas- 
sage through  the  lungs,  is  a  point  hardly  second  in  importance 
to  the  relative  composition  of  the  air  before  and  after  respi- 
ration. The  idea  enunciated  by  Mayow  about  two  hundred 
years  ago,  that  "there  is  something  in  the  air,  absolutely 

1  WILLIAM  STEVENS,  Observations  on  the  Healthy  and  Diseased  Properties  of  the 
Blood,  London,  1832,  p.  362;  and  Philosophical  Transactions,  1835. 

2  MILNE-EDWARDS,  Physiologic,  tome  i.,  p.  475. 

3  LONGET,  Traite  de  Physiologie,  Paris,  1861,  tome  i.,  p.  595.    Fernet  made  a 
great  number  of  experiments  on  the  influence  of  the  various  salts  contained  in  the 
serum  on  the  absorbing  power  of  the  blood  for  gases.     His  observations  had  par- 
ticular reference  to  carbonic  acid,  the  solubility  of  which  was  influenced  most  by 
saline  principles.    These  experiments  were  confirmed  and  extended  by  Lothar 
Meyer  (Die  Gase  des  Mutes). 


GASES   IN  VENOUS   AND  AETEEIAL   BLOOD.  457 

necessary  to  life,  which  is  conveyed  into  the  Uood" 1  excepting 
that  the  vivifying  principle  is  not  named  nor  its  other  prop- 
erties described,  expresses  what  we  now  consider  as  one  of 
the  two  great  principles  of  respiration.  This  is  even  more 
strictly  in  accordance  with  fact  than  the  idea  of  Lavoisier, 
who  supposed  that  all  the  chemical  processes  of  respiration 
took  place  in  the  lungs.  Mayow  also  described  the  evolution 
of  gas  from  blood  placed  in  a  vacuum.2  Many  observers 
have  since  succeeded  in  extracting  gases  from  the*  blood  by 
various  processes.  Sir  Humphry  Davy  induced  the  evolu- 
tion of  carbonic  acid  by  raising  arterial  blood  to  the  temper- 
ature of  200°  Fahr.,  and  venous  blood  to  a  temperature  of 
112° ; 3  Stevens,4  and  others,  disengaged  gas  by  displacement 
with  hydrogen,  nitrogen,  or  the  ordinary  atmosphere ;  but 
in  spite  of  this,  before  the  experiments  of  Magnus  in  1837, 
many  denied  the  existence  in  the  blood  of  any  free  gas  what- 
soever.5 

Magnus  made  some  experiments  upon  the  human  blood, 
extracting  the  gases  by  displacement  with  hydrogen ;  but  the 
observations  which  are  most  generally  referred  to  by  phys- 
iologists were  made  upon  the  blood  of  horses  and  calves, 
extracting  the  gases  by  the  air-pump,  and  giving  the  com- 
parative quantities  existing  in  the  arterial  and  venous  blood. 
These  experiments  were  of  great  value  as  settling  the  ques- 
tion of  the  existence  of  gases  in  the  blood,  either  in  a  free 
state,  or  very  loosely  combined  with  some  of  its  organic  con- 
stituents ;  and  until  very  recently  they  have  been  universally 

1  See  page  4 11,  note. 

2  See  quotation  in  MILNE-EDWARDS,  Physiologic,  tome  i.,  p.  438,  note. 

3  SIR  HUMPHRY  DAVY,  Works,  London,  1839,  vol.  i.,  pp.  77-79.     An  Essay 
on  Light,  Heat,  and  the  Combination  of  Light,  with  a  new  Theory  of  Respiration. 

4  Loc.  cit. 

6  Gmelin,  Mitscherlich,  and  Tiedemann  denied  the  existence  of  any  free  gases 
in  the  blood.  At  one  time  Dr.  John  Davy  held  the  same  opinion,  though  he 
finally  recognized  his  error,  and  succeeded  in  extracting  gas  from  the  blood  by 
means  of  the  air-pump  {Researches,  Physiological  and  Anatomical,  London, 
1839,  vol.  ii.,  p.  154). 


458  RESPIRATION. 

received  by  physiologists,  as  representing  the  relative  propor- 
tions of  the  gases  in  the  two  kinds  of  blood,  though  Magnus 
states  in  his  paper  that  he  does  not  think  he  succeeded  in 
extracting  all  the  gas  the  blood  contained.1  It  is  a  question 
of  the  last  importance,  as  Bearing  upon  our  comprehen- 
sion of  the  essential  processes  of  respiration,  to  be  able  to 
determine  the  relative  proportion  of  oxygen  and  carbonic 
acid  in  the  arterial  and  venous  blood.  Until  very  recently, 
our  ideas  On  this  subject  have  had  for  their  sole  experimental 
basis  the  observations  of  Magnus,  and  in  discussing  the  accu- 
racy of  the  modes  of  analysis  of  the  blood  for  gases  we  need 
take  no  account  of  any  experiments  anterior  to  his. 

Analysis  of  the  Blood  for  Gases. — There  are  certain  grave 
sources  of  error  in  the  method  employed  by  Magnus,  which 
render  his  observations  of  little  value,  except  as  demonstrating 
that  oxygen,  carbonic  acid,  and  nitrogen  may  be  extracted 
by  the  air-pump  from  both  arterial  and  venous  blood.  The 
only  source  of  error  in  the  results  which  he  fully  recognized 
lay  in  the  difficulty  in  extracting  the  entire  quantity  of  gas 
in  solution  ;  but  a  careful  study  of  his  paper  shows  another 
element  of  inaccuracy  which  is  even  more  important.  The 
relative  quantities  of  oxygen  and  carbonic  acid  in  any  single 
specimen  of  blood  present  great  variations,  dependent  upon 
the  length  of  time  that  the  blood  has  been  allowed  to  stand 
before  the  estimate  of  the  gases  is  made.  As  it  is  impossible 
to  make  this  estimate  immediately  after  the  blood  is  drawn, 
on  account  of  the  froth  produced  by  agitation  with  a  gas, 
when  the  method  by  displacement  is  employed,2  and  the 
bubbling  of  the  gas  when  extracted  by  the  air-pump,  this 

1  The  original  article  of  Magnus  is  published  in  the  Annalen  der  Physik  und 
Chemie  of  Poggendorff,  April,  1837,  and  is  translated  into  French  in  the  Ann.  de 
Chimie  et  de  Phys.  of  the  same  year. 

a  When  a  gas,  such  as  hydrogen,  which  is  not  contained  in  the  blood,  is  thor- 
oughly mixed  with  it  by  agitation  in  a  closed  vessel,  it  will  penetrate  the  liquid, 
and  displace,  or  drive  off,  all  the  free  gas  which  is  held  in  solution.  This  is  called 
the  method  of  analysis  by  displacement. 


ANALYSIS   OF  THE  BLOOD  FOE   GASES.  459 

objection  is  fatal.  It  is  necessary  to  wait  until  the  froth 
has  subsided  before  attempting  to  make  an  accurate  estimate 
of  the  volume  of  gas  given  off.  The  following  observation 
of  Magnus  illustrates  this  fact.  The  observation  was  on  the 
human  blood  six  hours  after  it  had  been  thoroughly  mixed 
with  hydrogen : 1 

Blood  of  Man.  .  Carbonic  acid. 

4-077  cubic  inches.  1-013  cubic  inches. 

3-650  rt  0-781  " 

3-838  "  1-355  " 

After  twenty-four  hours,  at  the  end  of  which  time  the 
blood  had  no  odor : 

4-077  cubic  inches.  1-517  cubic  inches. 

3-650  "  1-456  " 

3-833  "  2-075  " 

The  excess  of  carbonic  acid  found  twenty-four  hours  after, 
over  the  quantity  found  six  hours  after,  in  the  first  and  third 
specimens,  is  a  little  over  50  per  cent. ;  while  in  the  second 
specimen  it  is  very  nearly  100  per  cent. 

In  these  analyses  the  proportion  of  oxygen  is  not  given. 
The  question  naturally  arises  as  to  the  source  of  the  carbonic 
acid  which  was  evolved  during  the  last  eighteen  hours  of  the 
observation.  This  is  evident,  when  we  consider  one  of  the 
important  properties  of  the  blood.  A  number  of  years  ago, 
Spallanzani  demonstrated  that,  in  common  with  other  parts 
of  the  body,  fresh  blood  removed  from  the  body  has,  of  itself, 
the  property  of  consuming  oxygen ;  and  W.  F.  Edwards  has 
shown  that  the  blood  will  exhale  carbonic  acid.  In  1856, 
Harley,  by  a  series  of  ingenious  experiments,  found  that 
blood,  kept  in  contact  with  air  in  a  closed  vessel  for  twenty- 
four  hours,  consumed  oxygen  and  gave  off  carbonic  acid.2 

1  G.  MAGNUS,  Sur  les  Gas  que  contient  le  Sang :  Oxygene,  Azote  et  Acide  Car- 
bonique.     Annales  de  Chimie  et  de  Physique,  2me  serie,  tome  Ixv.,  1837,  p.  174. 

2  G.  HARLEY,  The  Chemistry  of  Respiration.     The  British  and  Foreign  Med 
ico-Chirurgical  Review,  July,  1856,  p.  328. 


4:60  KESPERATTON. 

• 

More  recently,  Bernard  ha$  shown  that  for  a  certain  time 
after  the  blood  is  drawn  from  the  vessels,  it  will  continue  to 
consume  oxygen  and  exhale  carbonic  acid.  If  all  the  car- 
bonic acid  be  removed  from  a  specimen  of  blood,  by  treating 
it  with  hydrogen,  and  it  be  allowed  to  stand  for  twenty-four 
hours,  another  portion  of  gas  can  be  removed  by  again  treat- 
ing it  with  hydrogen,  and  still  another  quantity  by  treating 
it  with  hydrogen  a  third  time.1 

From  these  facts  it  is  clear  that,  in  the  experiment  of 
Magnus,  the  excess  of  carbonic  acid  involved  a  post-mortem 
consumption  of  oxygen ;  and  no  analyses  made  in  the  ordi- 
nary way,  by  displacement  with  hydrogen,  or  by  the  air- 
pump,  in  which'  the  blood  must  necessarily  be  allowed  to 
remain  in  contact  with  oxygen  for  a  number  of  hours,  can  be 
accurate.  The  only  process  which  can  give  us  a  rigorous 
estimate  of  the  relative  quantities  of  oxygen  and  carbonic 
acid  in  the  blood  is  one  in  which  the  gases  can  be  estimated 
without  allowing  the  blood  to  stand,  or  in  which  the  forma- 
tion of  carbonic  acid  in  the  specimen,  at  the  expense  of  the 
oxygen,  is  prevented.  All  others  will  give  a  less  quantity  of 
oxygen  and  a  greater  quantity  of  carbonic  acid  than  exists  in 
the  blood  circulating  in  the  vessels,  or  immediately  after  it  is 
drawn  from  the  body. 

A  solution  of  this  important  and  difficult  problem  in  analy- 
sis of  the  blood  has  been  accomplished  by  Bernard.  This  ob- 
server made  a  great  number  of  experiments,  in  the  hope  of  dis- 
covering some  means  by  which  the  consumption  of  oxygen  by 
the  blood-corpuscles  could  be  arrested.2  He  found,  finally,  that 
carbonic  oxide,  one  of  the  most  active  of  the  poisonous  gases, 
had  a  remarkable  affinity  for  the  blood-corpuscles.  When 


1  BERNARD,  Lemons  sur  les  Proprietes  Physiologiques  et  les  Alterations  Patholo- 
giques  dcs  Liquides  de  VOrganisme,  Paris,  1859,  tome  i.,  p.  354  et  seq. 

8  Harley  (op.  cit.,  p.  334)  ascertained  that  a  few  drops  of  chloroform,  added  to 
the  fresh  blood,  greatly  diminished  the  activity  of  the  change  of  oxygen  into  car- 
bonic acid.  It  did  not  entirely  arrest  it,  however,  and  the  author  does  not  sug- 
gest its  use  in  quantitative  analyses  for  gases. 


ANALYSIS   OF  THE   BLOOD  FOR   GASES.  461 

taken  into  the  lungs,  it  is  absorbed  by  and  becomes  fixed  in 
the  corpuscles,  effectually  preventing  the  consumption  of  oxy- 
gen and  production  of  carbonic  acid,  which  normally  takes 
place  in  the  capillary  system,  and  which  is  one  of  the  indis- 
pensable conditions  of  nutrition.  We  have  already  referred 
to  the  mechanism  of  poisoning  by  the  inhalation  of  this  gas, 
by  its  fixation  in  the  blood-corpuscles,  their  consequent  par- 
alysis, and  the  arrest  of  their  function  as  respiratory  organs. 
As  it  is  the  continuance  of  this  transformation  of  oxygen  into 
carbonic  acid,  after  the  blood  is  drawn  from  the  vessels,  which 
interferes  with  the  ordinary  analysis  of  the  blood  for  gases, 
we  might  expect  to  extract  all  the  oxygen,  if  we  could  imme- 
diately saturate  the  blood  with  carbonic  oxide.  The  prelim- 
inary experiments  of  Bernard  on  this  point  are  conclusive. 
He  ascertained  that  by  mixing  carbonic  oxide  in  sufficient 
quantity  with  a  specimen  of  fresh  arterial  blood,  in  about 
two  hours,  all  the  oxygen  which  it  contained  was  dis- 
placed. Introducing  a  second  quantity  of  carbonic  oxide  af- 
ter two  hours,  and  leaving  it  in  contact  with  the  blood  for  an 
hour,  a  quantity  of  oxygen  was  removed,  so  small  that  it 
might  almost  be  disregarded.  A  third  experiment  on  the 
same  blood  failed  to  disengage  any  oxygen  or  carbonic  acid.1 

The  view  entertained  by  Bernard  of  the  action  of  car- 
bonic oxide  in  displacing  the  oxygen  of  the  blood  is,  that  the 
former  gas  has  a  remarkable  affinity  for  the  blood-corpuscles, 
in  which  nearly  all  the  oxygen  is  contained,  and  when 
brought  in  contact  with  them  unites  with  the  organic  matter, 
setting  free  the  oxygen,  in  the  same  way  that  the  acid  enter- 
ing into  the  composition  of  a  salt  is  set  free  by  any  other 
acid  which  has  a  stronger  affinity  for  the  base.  There  is 
every  reason  to  suppose  that  this  view  is  correct ;  as  carbonic 
oxide  is  much  less  soluble  than  oxygen,  and  as  it  only  has  the 
property  of  disengaging  this  gas  from  the  blood,  leaving  the 
other  gases  still  in  solution. 

As  carbonic  oxide  only  displaces  the  oxygen,  it  is  neces- 

1  BERNARD,  Liquidcs  de  V  Organisme^  tome  i.,  p.  373. 


4:62  RESPIRATION. 

sary  to  resort  to  some  other  process,  in  addition  to  this,  to 
disengage  the  other  gases  contained  in  the  blood.  It  is  only 
necessary  to  arrest  the  action  of  the  corpuscles  upon  the  oxy- 
gen, and  then  the  gases  may  be  set  free  by  the  air-pump,  or 
any  method  which  may  be  convenient.  The  method  adopted 
by  Bernard  for  the  disengagement  of  all  the  gases  contained 
in  the  blood  is  first  to  displace  the  oxygen  by  carbonic  oxide, 
using  about  two-thirds  of  gas  by  volume  to  one-third  of 
blood,  then  to  attach  the  tube  to  a  tube  of  mercury,  and  sub- 
ject the  blood  to  the  barometric  vacuum,  which  sets  free  the 
carbonic  acid  and  the  nitrogen.  The  results  obtained  by 
this  method  correspond  with  our  ideas  concerning  the  nature 
of  the  respiratory  process;  and  analyses  of  the  blood  taken 
at  different  periods  show  variations  in  the  quantities  of  oxy- 
gen in  the  arterial,  and  carbonic  acid  in  the  venous  blood, 
corresponding  with  some  of  the  variations  which  we  have 
noted  in  the  loss  of  oxygen  and  gain  of  carbonic  acid  in  the 
air,  in  respiration. 

The  analyses  of  Bernard,  who  obtained  from  fifteen  to 
twenty  per  cent,  of  oxygen  in  volume  from  the  arterial  blood, 
show  the  great  imperfection  of  the  process  employed  by 
Magnus,  who  obtained  from  the  arterial  blood  of  horses  and 
calves  a  mean  of  but  2  '44:  per  cent,  of  oxygen.  It  does 
not  seem  necessary,  therefore,  to  discuss  the  criticisms  of  the 
results  obtained  by  Magnus  which  were  made  by  Gay-Lussac 
and  Magendie,  soon  after  their  publication,  and  more  recent- 
ly by  Harley  and  others.1 

1  To  Magnus  belongs  the  credit  of  demonstrating  the  important  fact  that  oxy- 
gen, carbonic  acid,  and  nitrogen  can  be  extracted  from  the  blood  by  removing  the 
atmospheric  pressure.  Before  his  observations,  Gmelin,  Mitscherlich,  and  Tiede- 
mann  placed  venous  blood  in  a  tube  over  mercury,  in  the  receiver  of  an  air-pump, 
and  by  removing  fhe  pressure  as  far  as  possible,  caused  the  mercury  to  descend. 
On  admitting  air  into  the  receiver  and  restoring  the  pressure,  the  mercury 
ascended,  with  the  blood,  again  filling  the  tube  completely.  From  this  they 
reasoned  that  there  was  no  free  carbonic  acid  in  the  blood.  By  passing  up  a 
little  acetic  acid,  carbonic  acid  was  set  free,  which  led  them  to  believe  that  all 
the  carbonic  acid  was  in  combination.  Magnus  showed  that  the  reason  why 
other  observers  had  failed  to  extract  gas  by  means  of  the  air-pump  was,  that  the 


ANALYSIS   OF  THE  BLOOD  TOR  GASES.  463 

Bernard's  experiments  were  made  chiefly  on  dogs,  and 
had  especial  reference  to  the  proportion  of  oxygen  in  the 

rarefaction  of  the  air  was  not  carried  sufficiently  far.  J.  Davy,  in  his  second 
experiments,  recognized  this  fault  in  his  first  observations.  As  the  results  ob- 
tained by  Magnus  are  generally  quoted  and  received  in  works  on  physiology,  we 
give  the  table,  which  is  taken  from  the  translation  of  his  original  article  in  the 
Annales  de  Chimie  et  de  Physique  (loc.  cit.~).  We  have  not  thought  it  worth  while 
to  reduce  the  volumes  from  cubic  centimetres  to  cubic  inches,  as  we  add  the 
percentage  of  gas  in  volume,  which  is  not  given  by  Magnus. 

(  5-4  of  carbonic  acid,  or  4'32  per  cent. 

Blood  of  horse 125  c.c.  gave  9*8  c.c.  of  gas-(  1*9  of  oxygen,  or  1'52  per  cent. 

(  2-5  of  nitrogen,  or  2'00     " 

Venous  blood  of  the  same,  )  i  8-8  of  carbonic  acid,  or  4-29  per  cent 

four  days  after  the  tak-  V205  c.c.  gave  12'2  c.c.  of  gas-^  2'3  of  oxygen,  or  1'12  per  cent, 
ing  of  arterial  blood. . . .  \  / 1-1  of  nitrogen,  or  0'54     " 

( lO'O  of  carbonic  acid,  or  5'12  per  ct. 

The  same  blood 195  c.c.  gave  14-2  c.c.  of  gas-  2-5  of  oxygen,  or  1-28  per  cent 

|  1-7  of  nitrogen,  or  0-82    " 

Arterial  blood  of  a  horse  )  (  10-7  of  carbonic  acid,  or  8'23  per  ct. 

very  old,  but  in  good  >130  c.c.  gave  16'3  c.c.  of  gas-<  4'1  of  oxygen,  or  3'15  per  cent 

health )  ( 1-5  of  nitrogen,  or  1 -15     " 

(  7'0  of  carbonic  acid,  or  5'74  per  cent 

The  same  blood 122  c.c.  gave  10-2  c.c.  of  gas-C  2-2  of  oxygen,  or  1'SO  per  cent 

( 1  -0  of  nitrogen,  or  0'82    " 

Yenous  blood  of  the  same  )  (  12'4  of  carbonic  acid,  or  T'29  per  ct. 

old  horse,  drawn  three  VlTO  c.c.  gave  18-9  c.c.  of  gas-(  2'5  of  oxygen,  or  1-47  per  cent. 

days  after )  (  4-0  of  nitrogen,  or  2-35     " 

I  9-4  of  carbonic  acid,  or  7'64  per  cent 

Arterial  blood  of  calf 123  c.c.  gave  14'5  c  c.  of  gas^  3-5  of  oxygen,  or  2-84  per  cent. 

/ 1-6  of  nitrogen,  or  1-30     " 

(  7'0  of  carbonic  acid,  or  6*49  per  cent. 

The  same  blood 108  c.c.  gave  12-6  c.c.  of  gas-<  3-0  of  oxygen,  or  2-87  per  cent 

(  2-6  of  nitrogen,  or  2-40    u 

Yenous  blood  of  the  same  )  1 10-2  of  carbonic  acid,  or  6'66  per  ct 

calf,  taken   four    days  >-153  c.c.  gave  13  3  c.c.  of  gas-<  1-8  of  oxygen,  or  1-17  per  cent 

after. )  / 1-3  of  nitrogen,  or  0'85     " 

(  6'1  of  carbonic  acid,  or  4'35  per  cent 

The  same  blood 140  c.c.  gave  7'7  c.c.  of  gasX  I'O  of  oxygen,  or  0'71  per  cent 

(  0'6  of  nitrogen,  or  0'43     " 

We  have  given  this  table  in  full,  and  calculated  the  percentage  of  gas  to  the 
blood  in  each  observation,  because  it  is  a  common  impression  that  the  observa- 
tions of  Magnus  show  a  greater  proportion  of  oxygen  in  the  arterial  blood,  and  a 
greater  proportion  of  carbonic  acid  in  the  venous  blood.  This  is  not  the  fact. 
The  table  shows  that  the  proportion  of  all  gases  is  greater  in  the  arterial  blood, 
and  that  the  proportion  of  carbonic  acid  to  the  oxygen  is  greater  in  the  venous 
blood ;  but  while  the  percentage  of  oxygen  is  greater  in  the  arterial  blood,  there 
is  also  a  larger  percentage  of  carbonic  acid.  In  the  specimens  of  arterial  blood 
examined,  the  mean  proportion  of  oxygen  was  2*44  per  cent.,  and  of  carbonic 
acid  6 '48  per  cent.  In  the  venous  blood,  the  mean  proportion  of  oxygen  was 
1'15  per  cent.,  and  of  carbonic  acid,  6*54  per  cent.  It  is  difficult  to  reconcile  an 
analysis,  showing  a  greater  absolute  quantity  of  carbonic  acid  in  arterial  than  in 
venous  blood,  with  our  settled  and  well-sustained  ideas  regarding  the  processes 
of  respiration.  A  glance  at  the  wide  differences  in  the  different  analyses  of  speci- 
mens of  the  same  blood  shows  that  there  must  have  been  some  grave  error 
in  the  process. 


464  RESPIRATION. 

blood.  As  far  as  we  know,  no  analyses  of  the  human  blood 
have  jet  been  made  by  his  method.  In  two  specimens  taken 
from  a  dog  in  good  condition,  a  specimen  of  arterial  blood, 
drawn  from  the  vessels  by  a  syringe  and  put  in  contact 
with  carbonic  oxide  without»being  exposed  to  the  air,  was 
found  to  contain  18*28  per  cent.,  and  a  specimen  of  venous 
blood,  taken  in  the  same  way,  8*42  per  cent.,  in  volume,  of 
oxygen.1  The  proportion  of  gases  in  the  blood  is  found  to 
vary  very  considerably  under  different  conditions  of  the  sys- 
tem, particularly  with  reference  to  the  digestive  process. 
The  following  are  the  general  results  of  later  observations, 
showing  the  differences  and  variations  in  the  proportions  of 
all  the  gases,  in  arterial  and  venous  blood.2 

Arterial  Blood^  while  an  animal  is  fasting,  contains  from 
nine  to  eleven  parts  per  hundred  of  oxygen.  In  full  digestion, 
the  proportion  is  raised  to  seventeen,  eighteen,  or  even  twenty 
parts  per  hundred.  The  proportion  varies  in  different  animals ; 
being  much  greater,  for  example,  in  birds  than  in  mammals. 
The  quantity  of  carbonic  acid  is  even  more  variable  than 
the  quantity  of  oxygen.  During  digestion  there  are  from 
five  to  six  parts  per  hundred  of  free  carbonic  acid  in  the 
arterial  blood.  During  the  intervals  of  digestion  this  quan- 
tity is  reduced  to  almost  nothing ;  and  after  fasting  for  twenty- 
four  hours,  frequently  not  a  trace  is  to  ~be  discovered. 

Venous  Blood  always  contains  a  large  quantity  of  car- 
bonic acid,  both  free  in  solution,  and  combined  in  the  form 
of  carbonates  and  bicarbonates.  This  quantity  varies  in  dif- 
ferent parts  of  the  venous  system,  and  bears  a  relation  to  the 
color  of  the  blood.  It  is  well  known  that  the  venous  blood 
coming  from  some  glands  is  dark  during  the  intervals  of 
secretion,  and  nearly  as  red  as  arterial  blood  during  their 
functional  activity.  In  the  venous  blood  from  the  sub-max- 

1  Loc.  cit.,  p.  367. 

2  These  results  were  given  in  a  course  of  lectures  which  we  had  the  privilege 
of  hearing  at  the  College  of  France  in  the  summer  of  1861,  and  which  have  not 
yet  been  published. 


NITROGEN   OF   THE   BLOOD.  465 

illary  gland  of  a  dog,  Bernard  found  18*07  per  cent,  of  car- 
bonic acid  during  repose,  and  1O14  per  cent,  during  secre- 
tion. The  blood  coming  from  the  muscles  is  the  darkest  in 
the  body,  and  contains  the  greatest  quantity  of  free  carbonic 
acid. 

The  quantity  of  free  carbonic  acid  is  immensely  increased 
in  the  venous  blood  during  digestion.  It  is  owing  to  this 
fact  that  the  gas  then  exists  in  the  arterial  blood.  During 
the  intervals  of  digestion,  the  quantity  is  so  small  that  the 
lungs  are  capable  of  completely  eliminating  it,  and  none 
passes  into  the  arteries  ;  but  during  digestion,  the  proportion 
is  so  much  greater,  that  for  a  time  it  cannot  be  entirely  re- 
moved, and  a  part  finds  its  way  into  the  arterial  system. 

These  facts  coincide  with  the  views  which  are  now  held 
regarding  the  essential  processes  of  respiration.  The  blood 
going  to  the  lungs  ordinarily  contains  carbonic  acid,  and  no 
oxygen ;  for  during  the  intervals  of  digestion,  there  is  only 
enough  oxygen  taken  up  by  the  blood  to  supply  the  wants  of 
the  system.  In  the  lungs,  carbonic  acid  is  given  off,  appear- 
ing in  the  expired  air,  and  the  oxygen  which  disappears  from 
the  air  is  carried  away  by  the  arterial  blood.  Under  some 
conditions,  and  particularly  during  the  height  of  the  digestive 
process,  the  quantity  of  oxygen  absorbed  is  largely  increased, 
and  so  much  may  exist  in  the  arterial  blood  that  a  small  por- 
tion passes  into  the  veins.  At  the  same  time  the  production  of 
carbonic  acid  is  increased  in  activity,  and  it  may  exist  in  such 
quantity  in  the  venous  blood,  as  temporarily  to  pass  in  small 
quantity  into  the  arteries. 

Nitrogen  of  the  Blood. — As  far  as  is  known,  nitrogen  has 
no  important  office  in  the  process  of  respiration.  There  is 
generally  a  slight  exhalation  of  this  gas  by  the  lungs,  and 
the  analyses  of  Magnus  and  others  have  demonstrated  its 
existence  in  solution  in  the  blood.  Magnus  found  generally 
a  larger  proportion  in  the  arterial  than  in  venous  blood, 
though  in  one  instance  there  was  a  larger  proportion  in  the 
30 


466  RESPIRATION. 

venous  blood.  It  is  not  absolutely  certain  whether  the  ni- 
trogen which  exists  in  the  blood  is  derived  from  the  air  or 
from  the  tissues.  Its  almost  constant  exhalation  in  the  ex- 
pired air  would  lead  to  the  supposition  that  it  is  produced  in 
small  quantity  in  the  system,»or  supplied  by  the  food.  Ac- 
cording to  Bernard,  the  quantity  of  nitrogen  in  the  arterial 
blood  is  from  two  to  five  parts  per  thousand,  but  it  is  present 
in  very  much  larger  quantity  in  the  venous  blood.1  There 
is  no  evidence  that  nitrogen  enters  into  combination  with  the 
blood-corpuscles;  it  exists  simply  in  solution  in  the  blood, 
which  is  capable  of  absorbing  about  ten  times  as  much  as 
pure  water.2  Nothing  is  known  with  regard  to  the  rela- 
tions of  the  free  nitrogen  of  the  blood  to  the  processes  of 
nutrition. 

Condition  of  the  Gases  in  the  Blood. — It  is  now  pretty 
generally  admitted  that  the  oxygen  of  the  blood  exists,  not 
in  simple  solution,  but  in  a  condition  of  feeble  combination 
with  certain  of  the  constituents  of  the  blood-corpuscles.3  It 
is  clearly  demonstrated  that  the  corpuscles  are  the  elements 
which  fix  the  greatest  quantity  of  this  gas.  Carbonic  oxide, 
which  has  a  great  affinity  for  the  corpuscles,  displaces  almost 
immediately  all  the  oxygen  which  the  blood  contains.  When 
the  corpuscles  are  destroyed,  as  they  may  be  readily  by  re- 
ceiving fresh  blood  into  a  quantity  of  pure  water,  the  red 
color  is  instantly  changed  to  black.  Oxygen  in  the  blood 
bears  a  closer  relation  to  the  corpuscles  than  that  of  mere  solu- 

1  Unpublished  lectures  delivered  at  the  College  of  France  in  the  summer 
of  1861. 

2  MAGNUS,  loc.  cit. 

3  It  is  not  settled  which  of  the  constituents  of  the  blood-corpuscles  has  the 
greatest  affinity  for  oxygen.    It  has  been  supposed  to  be  combined  especially  with 
the  coloring  matter ;  but  experiments  on  this  point  are  contradictory.     Lehmann 
noticed  no  difference  in  the  color  of  a  solution  of  blood-crystals  treated  with  oxy- 
gen, and  the  same  solution  treated  with  carbonic  acid ;  the  only  difference  was 
that  the  latter  became  turbid  (Physiological  Chem.,  Am.  ed.,  vol.  i.,  p.  573). 
Meckel  made  some  experiments  in  which  "  hsematoglobulin  "  was  changed  to  a 
bright  red  by  oxygen,  and  to  a  bluish  red  by  carbonic  acid  (Ibid.,  p.  674). 


CONDITION   OF  THE   GASES   IN   THE   BLOOD.  467 

tion.  The  proportion  which  they  are  capable  of  containing 
is  to  a  certain  degree  absolute,  and  not  dependent  upon  phys- 
ical conditions,  such  as  pressure,  which  invariably  have  an 
influence  on  the  proportion  of  gas  merely  held  in  solution  by 
liquids.  The  proportion  of  oxygen  in  the  blood  cannot  be 
increased  by  pressure,  nor  is  it  diminished  by  reduction 
of  the  pressure,  until  it  approaches  a  vacuum.1  The  fact 
that  the  blood-corpuscles  are  capable  of  consuming  oxygen 
and  giving  off  carbonic  acid  is  an  additional  argument  in 
favor  of  the  union  of  these  anatomical  elements  with  the 
gas,  though  this  union  is  very  feeble  and  easily  disturbed. 
The  plasma  will  absorb  a  certain  quantity  of  oxygen,  and  its 
action  in  respiration  seems  to  be  intermediate ;  it  first  takes 
oxygen  from  the  air  and  then  gives  it  up  to  the  corpuscles. 

Carbonic  acid  is  more  easily  exhaled  from  the  blood  than 
oxygen.  It  was  this  principle  which  was  obtained  by  those 
who  first  succeeded  in  extracting  gas  from  the  blood.  While 
there  is  every  reason  to  suppose  that  oxygen  is  in  combina- 
tion with  the  blood-corpuscles,  carbonic  acid  seems  to  be  in  a 
condition  of  simple  solution,  and  is  contained  more  especially 
in  the  plasma.  What  may  be  considered  as  the  free  carbonic 
acid  of  the  blood  behaves  in  all  regards  like  a  gas  simply  held 
in  solution.  The  view  that  it  is  held  in  solution  chiefly  in  the 
plasma  is  sustained  by  the  fact  that  serum  will  absorb  more 
carbonic  acid  than  an  equal  volume  of  defibrinated  blood.2 

Liebig  has  shown  that  the  phosphate  of  soda,  one  of  the 
constituents  of  the  blood,  influences  to  a  remarkable  degree 
the  quantity  of  carbonic  acid  which  can  be  held  in  solution 
by  any  liquid.  One  hundredth  of  a  part  of  this  salt  in  pure 
water  will  double  its  capacity  for  dissolving  carbonic  acid.3 

1  The  fact  that  oxygen  is  exhaled  from  the  blood  in  vacua  is  not  an  argument 
against  the  view  that  it  enters  into  feeble  combination  with  the  blood-corpuscles ; 
for  it  is  well  known  that  many  distinctly  recognized  chemical  combinations  are 
disturbed  by  the  same  means.     For  example,  a  vacuum  is  capable  of  disengaging 
from  some  of  the  bicarbonates  one  equivalent  of  carbonic  acid. 

2  LONGET,  Traite  de  Physiologic,  Paris,  1861,  tome  i.,  p.  494. 

3  MILNE-EDWARDS,  Physiologic,  tome  i.,  p.  471. 


468  RESPIRATION. 

When  carbonic  acid  is  formed  by  the  blood,  after  it  is  drawn 
from  the  body,  it  is  immediately  exhaled,  at  least  in  part. 
When  blood  is  in  contact  with  a  certain  quantity  of  air,  oxy- 
gen is  consumed  and  carbonic  acid  is  exhaled.  The  fact  that 
carbonic  oxide,  which  has  sueti  a  remarkable  affinity  for  the 
corpuscles,  displaces  oxygen  almost  exclusively,  is  another 
argument  in  favor  of  the  view  that  the  carbonic  acid  is  con- 
tained mainly  in  the  plasma. 

A  portion  of  the  carbonic  acid  which  is  formed  by  the 
system  unites  with  the  carbonates  in  the  blood,  particularly 
the  carbonate  of  soda,  to  form  bicarbonates,  is  carried  to  the 
lungs,  and  there  set  free  by  the  pneumic  acid.  It  here  exists 
in  so  loose  a  condition  of  combination,  that  it  may  be  dis- 
engaged by  treating  the  blood  with  inert  gases,  or  putting  it 
under  the  receiver  of  an  air-pump. 

The  carbonic  acid  which  is  formed  in  the  tissues,  and  taken 
up  by  the  blood  in  its  passage  through  the  capillaries,  exists 
in  this  fluid  in  two  forms  :  one,  in  simple  solution,  chiefly  in 
the  plasma ;  and  the  other,  in  a  state  of  such  loose  chemical 
combination  in  the  bicarbonates,  that  it  may  be  disengaged 
by  displacement  by  another  gas,  and  is  readily  set  free  by 
pneumic  acid.  This  gas  is  a  product  of  excretion,  and  is  not 
engaged  in  any  of  the  vital  functions ;  while  oxygen,  which 
has  an  all-important  function  to  perform,  unites  immediately 
with  the  blood-corpuscles,  and  is  not  easily  disengaged, 
except  when  it  undergoes  transformation  in  the  process  of 
nutrition.  It  is  certain  that  all  the  carbonic  acid  in  the  blood 
is  not  in  combination  with  bases,  for  the  proportion  of  salts 
is  not  sufficient  to  account  for  all  the  carbonic  acid  that  can 
be  disengaged. 

In  addition  to  this  excrementitious  carbonic  acid,  there 
is  another  portion  which  is  a  permanent  constituent  of  the 
blood,  in  the  carbonates,  and  cannot  be  set  free  without  the 
use  of  reagents. 

Nitrogen  exists  in  the  blood  in  the  same  condition  of  solu- 

o 

tion  in  the  plasma  as  carbonic  acid. 


MECHANISM   OF   THE   INTEKCHANGE    OF    GASES.  469 

Mechanism  of  the  Interchange  of  Gases  between  the  Blood 
and  the  Air,  in  the  Lungs. — The  gases  from  tlie  air  pass  into 
the  blood,  and  the  gases  of  the  blood  are  exhaled  through 
the  delicate  membrane  which .  separates  these  two  fluids,  in 
accordance  with  laws  which  are  now  well  understood.  The 
first  to  point  out  the  power  of  gases  thus  to  penetrate  and 
pass  through  membranes  was  the  late  Dr.  J.  K.  Mitchell,  of 
Philadelphia.1  His  attention  was  first  directed  to  this  subject 
by  noticing  the  escape  of  gas  from  gum-elastic  balloons  filled 
with  hydrogen.  In  order  to  satisfy  himself  that  the  gas 
passed  through  the  membrane  independently  of  pressure,  he 
put  different  gases  in  wide-mouthed  bottles  covered  with  gum- 
elastic,  and  by  a  series  of  ingenious  experiments,  which  have 
become  so  common  that  it  is  unnecessary  to  describe  them 
in  detail,  extended  Dutrochet's  law  of  endosmosis  and  exos- 
mosis  to  the  gases.  He  demonstrated  the  same  phenomena 
when  he  used  thin  animal  membranes  instead  of  the  gum- 
elastic,  and  found  that  the  more  recent  the  membrane,  the 
more  rapid  was  the  action.  The  rapidity  of  transmission  was 
found  to  be  very  great  in  living  animals.  Observations  on 
the  lungs  of  the  snapping  turtle,  filled  with  air  and  placed  in 
an  atmosphere  of  carbonic  acid  or  nitrous  oxide,  showed  a 
very  rapid  passage  of  gas  from  the  exterior  to  the  interior. 
Dr.  Mitchell  recognized  the  passage  of  gases  through  mem- 
branes into  liquids,  and  the  exhalation  of  gases  which  were 
in  solution  in  these  liquids.  He  noted  this  action  in  the  ab- 
sorption of  oxygen  and  the  exhalation  of  carbonic  acid  in  the 
lungs ;  though  he  fell  into  the  error  of  supposing  that  there 
was  no  carbonic  acid  in  solution  in  the  blood,  and  that  it  was 
exhaled  as  soon  as  formed.2  A  few  years  later,  Dr.  Rogers, 
of  Philadelphia,  enclosed  a  fresh  pig's  bladder,  filled  with 

1  On  the  Peneirativeness  of  Fluids.  By  J.  K.  MITCHELL,  M.D.,  Lecturer  on 
Medical  Chemistry  in  the  Philadelphia  Medical  Institute.  American  Journal  of 
the  Medical  Sciences,  Nov.,  1830,  p.  36. 


470  RESPIRATION. 

venous  blood,  in  a  bell-glass  of  oxygen.1  In  two  hours  a 
quantity  of  oxygen  had  disappeared,  and  a  large  quantity  of 
carbonic  acid  had  made  its  appearance.  Dr.  Rogers  is  fre- 
quently referred  to  as  the  first  to  demonstrate  the  passage  of 
gases  through  animal  membranes  to  and  from  the  blood. 
The  credit  of  this  is  due  to  Mitchell,  whose  paper  was  pub- 
lished in  1830,  while  the  experiments  of  Rogers  were  pub- 
lished in  1836. 

We  have  already  seen  that  the  blood  is  exposed  to  the  air 
in  the  lungs,  separated  from  it  only  by  a  very  delicate  mern-  • 
brane,  over  an  immense  surface.  The  membrane,  far  from 
interfering  with  the  interchange  of  gases,  actually  favors  it ; 
and  thus,  in  obedience  to  the  laws  which  regulate  endosmosis 
between  gases  and  liquids,  the  oxygen  is  continually  passing 
into  the  blood,  and  the  free  carbonic  acid  is  exhaled. 

General  Differences  in  the  Composition  of  Arterial  and 
Venous  Blood. — All  observers  agree  that  there  are  certain 
marked  differences  in  the  composition  of  arterial  and  venous 
blood,  aside  from  their  free  gases.  The  arterial  blood  con- 
tains less  water,  and  is  richer  in  organic,  and  most  inorganic, 
constituents  than  the  venous  blood.  It  also  contains  a  greater 
proportion  of  corpuscles,  fibrin,  and  inorganic  salts.  It  is 
more  coagulable,  and  offers  a  larger  and  firmer  clot  than 
venous  blood.  Numerous  analyses  have  failed  to  detect  a 
constant  difference  in  the  proportion  of  albumen  ;  sometimes 
the  proportion  is  greater  in  the  venou%  and  sometimes  in  the 
arterial  blood.  The  only  principles  which  are  constantly 
more  abundant  in  venous  blood  are  water  and  the  alkaline 
carbonates.  10,000  parts  of  venous  blood  contained  12*3 
parts  of  carbonic  acid  combined,  and  the  same  quantity  of 
arterial  blood  contained  but  8*3  parts.2  The  deficiency  of 
water  in  the  blood  which  comes  from  the  lungs  is  readily  ex- 
plained by  the  escape  of  watery  vapor  in  the  expired  air. 

1  Experiments  on  the  Blood,  etc.   By  ROBERT  E.  EOGERS,  M.D.,  of  Philadelphia. 
American  Journal  of  the  Medical  Sciences,  August,  1836,  p.  296, 
9  LONGET,  op,  cit.,  tome  i.,  p.  584. 


DIFFERENCES   DT   COMPOSITION   OF  BLOOD.  4Y1 

An  important  distinction  between  arterial  and  venous 
blood  is  one  to  which  we  have  already  incidentally  alluded, 
viz.,  that  the  former  has  a  uniform  composition  in  all  parts  of 
the  arterial  system,  while  the  composition  of  the  latter  varies 
very  much  in  the  blood  coming  from  different  organs.  Arte- 
rial blood  is  capable  of  carrying  on  the  processes  of  nutrition ; 
while  venous  blood  ia  not,  and  cannot  even  circulate  freely 
in  the  systemic  capillaries. 


CHAPTEE  XIY. 


ETC. 


Vriews  of  physiologists  anterior  to  the  time  of  Lavoisier — Relations  of  the  con- 
sumption of  oxygen  to  nutrition — Relations  of  the  exhalation  of  carbonic  acid 
to  nutrition — Essential  processes  of  respiration— The  respiratory  sense,  or 
want  on  the  part  of  the  system  which  induces  the  respiratory  movements — 
Location  of  the  respiratory  sense  in  the  general  system — Sense  of  suffocation 
— Respiratory  efforts  before  birth — Cutaneous  respiration — Asphyxia. 

IT  has  been  demonstrated  that  all  tissues,  so  long  as  they 
retain  their  absolute  integrity  of  composition,  have  the  prop- 
erty of  appropriating  oxygen  and  exhaling  carbonic  acid,  in- 
dependently of  the  presence  of  blood ;  and  that  the  arterial 
blood  carries  oxygen  from  the  lungs  to  the  tissues,  there  gives 
it  up,  and  receives  carbonic  acid,  which  is  carried  by  the 
venous  blood  to  the  lungs,  to  be  exhaled.  From  this  fact 
alone,  it  is  more  than  probable  that  respiration  is  inseparably 
connected  with  the  general  act  of  nutrition.  Its  processes 
must  be  studied,  therefore,  as  they  take  place  in  the  tissues  and 
organs  of  the  body.  In  the  present  state  of  the  science,  the 
questions  which  naturally  arise  in  connection  with  the  essen 
tial  processes  of  respiration  are : 

1.  In  what  way  is  oxygen  consumed  in  the  system  ? 

2.  How  is  carbonic  acid  produced  by  the  system  ? 

3.  "What  is  the  nature  of  the  processes  which  take  place 
between  the  disappearance  of  oxygen  and  the  evolution  of 
carbonic  acid  ? 

When  these  questions  are  satisfactorily  answered,  we  shall 
understand  the  essence  of  respiration ;  but  in  reasoning  on  this 


RELATIONS   TO  NUTRITION.  473 

subject,  we  must  not  fall  into  the  error  of  assimilating  the 
respiratory  phenomena  too  closely  to  those  with  which  we  are 
acquainted  as  they  occur  in  inorganic  bodies.  It  must  be  re- 
membered that  in  the  organism  we  are  dealing  with  principles 
which  have  the  remarkable  property  of  self-regeneration; 
and  which,  as  a  simple  condition  of  vital  existence,  consume 
oxygen,  when  it  is  presented  to  them,  and  exhale  carbonic 
acid.  Without  a  proper  supply  of  oxygen,  the  tissues  die, 
lose  these  peculiar  properties,  and  finally  disappear  by  putre- 
factive decomposition.  This  consumption  of  oxygen  cannot 
be  regarded  in  any  other  light  than  as  the  appropriation  by 
a  living  part,  of  an  element  necessary  to  supply  waste ;  in 
the  same  way  as  those  materials  which  are  ordinarily  called 
nutritive  are  appropriated.  That  waste  is  continually  going 
on  there  can  be  no  doubt;  and  as  the  production  of  urea, 
creatine,  creatinine,  cholesterine,  etc.,  is  to  a  certain  extent 
independent  of  the  absorption  of  food,  so  the  production  of 
carbonic  acid  is  to  a  certain  extent  independent  of  the  ab- 
sorption of  oxygen.  This  has  been  fully  demonstrated  by 
the  experiments  of  Spallanzani,  Edwards,  Geo.  Liebig,  and 
others,  who  have  noted  the  exhalation  of  carbonic  acid  in  at- 
mospheres which  contained  no  oxygen.  How  different  are 
these  phenomena  from  those  which  attend  combinations  and 
decompositions  of  inorganic  matters !  As  an  example,  let 
oxygen  be  brought  in  contact,  under  proper  conditions,  with 
iron.  Under  these  circumstances,  a  union  of  iron  and  oxy- 
gen takes  place,  and  a  new  substance,  oxide  of  iron,  is  formed, 
which  has  peculiar  and  distinct  properties.  In  the  same 
way,  carbonic  acid  may  be  disengaged  from  its  combinations 
by  the  action  of  a  stronger  acid,  which  unites  with  the  base 
and  forms  a  new  substance,  in  no  way  resembling  the  origi- 
nal salt.  To  make  the  contrast  still  more  striking,  let  a  hy 
dro-carbon,  like  fat,  be  heated  in  oxygen  or  the  air,  until  it 
undergoes  combustion ;  it  is  then  changed  into  carbonic  acid 
and  water,  by  a  definite  chemical  reaction,  and  is  utterly  de- 
stroyed as  fat. 


RESPIRATION. 

In  the  living  body  the  organic  nitrogenized  principles  are 
in  a  condition  of  continual  change ;  breaking  down,  and  form- 
ing various  excrementitious  principles,  at  the  head  of  which 
may  be  placed  carbonic  acid.  It  is  essential  to  life  that  these 
principles  be  maintained  in  their  chemical  integrity,  which 
requires  a  supply  of  fresh  matter  as  food,  and  above  all  a 
supply  of  oxygen.  We  put  ourselves  in  the  position  of  ig- 
noring well-established  facts  and  principles  when  we  assimi- 
late without  reserve  the  process  of  the  consumption  of  oxygen 
and  production  of  carbonic  acid  by  living  organic  bodies,  to 
simple  combustion  of  sugar  or  fat.  The  ancients  saw  that 
the  breath  was  warmer  than  the  surrounding  air,  that  in  the 
lungs  the  air  took  heat  from  the  body  ;  and  as  they  knew  of 
no  other  changes  in  the  air  produced  by  respiration,  they  as- 
sumed that  its  object  was  simply  to  cool  the  blood.  Lavoisier 
discovered  that  the  air,  containing  oxygen,  lost  a  portion  of 
this  principle  in  respiration,  and  gained  carbonic  acid  and 
watery  vapor.  He  saw  that  this  might  be  imitated  by  the 
combustion  of  hydro-carbons,  such  as  exist  in  the  blood.  He 
called  respiration  a  slow  combustion,  and  regarded  as  its  prin- 
cipal office  the  maintenance  of  animal  temperature.  "When 
it  was  shown  by  analyses  of  the  blood  for  gases,  that  oxygen 
was  not  consumed  in  the  lungs,  but  taken  up  by  the  circulating 
fluid,  and  carried  all  over  the  body,  and  that  carbonic  acid 
was  brought  from  all  parts  by  the  blood  to  the  lungs,  these 
facts,  taken  in  connection  with  the  fact  that  the  tissues  have 
the  property  of  consuming  oxygen  and  exhaling  carbonic 
acid,  led  physiologists  to  change  the  location  of  the  combus- 
tive  process  from  the  lungs  to  the  tissues. 

We  cannot  stop  at  this  point.  Now  it  is  known  that  the 
organic  principles  of  the  body,  w^hich  form  the  basis  of  all 
tissues  and  organs,  are  continually  undergoing  change  as  a 
condition  of  existence;  that  they  do  not  unite  with  any 
substance  in  definite  chemical  proportions,  but  their  par- 
ticles, after  a  certain  period  of  existence,  degenerate  into 
excrementitieus  substances,  and  they  are  regenerated  by  an 


RELATIONS   TO   NUTRITION.  4/T5 

appropriation  and  change  of  materials  furnished  by  the  blood. 
As  far  as  the  respiration  of  these  parts  is  concerned,  we  can 
only  say,  that  in  this  process,  carbonic  acid  is  produced  and 
oxygen  is  consumed.  These  facts  show  that  respiration  is 
essentially  a  phenomenon  of  nutrition,  possessing  a  degree 
of  complexity  equal  to  that  of  the  other  nutritive  processes. 
It  must  be  acknowledged  that  thus  far  its  cause  and  intimate 
nature  have  eluded  investigation.  In  respiration  by  the  tis- 
sues, no  one  has  yet  been  able  to  give  the  cause  of  the  ab- 
sorption of  oxygen  or  the  exhalation  of  carbonic  acid ;  or  to 
demonstrate  the  condition  in  which  oxygen  exists  when  once 
appropriated,  or  the  particular  changes  which  take  place, 
and  the  principles  which  are  lost,  in  the  formation  of  carbonic 
acid. 

The  views  of  physiologists  with  regard  to  the  essential 
processes  of  respiration,  before  the  time  of  Lavoisier,  have 
barely  an  historical  interest  at  the  present  day ;  except  the 
remarkable  idea  of  Mayow,  which  comprehended  nearly  the 
whole  process,  and  which  was  unnoticed  for  about  a  hundred 
years.1  It  is  not  our  object  to  dwell  upon  the  various  theo- 
ries which  have  been  proposed  from  time  to  time,  or  even 
to  fully  discuss,  in  this  connection,  the  combustion  theory  as 
proposed  by  Lavoisier,  and  modified  by  Liebig  and  others. 
Though  this  theory  is  nominally  received  by  many  physiolo- 
gists of  the  present  day,  it  will  be  found  that  most  of  them, 
in  accordance  with  the  facts  which  have  since  been  developed, 
really  regard  respiration  as  connected  with  nutrition.  They 
only  differ  from  those  who  reject  the  combustion  theory,  in 
their  definition  of  the  term  combustion.  Lavoisier  regarded 
respiration  as  a  slow  combustion  of  carbon  and  hydrogen ; 
and  if  every  rapid  or  slow  combination  of  oxygen  with  any 
other  body  be  considered  a  combustion,  this  view  is  abso- 
lutely correct,  and  was  proven  when  it  was  shown  that  oxygen 
united  with  any  of  the  tissues.  Longet  says  that  since  the 
time  of  Lavoisier  it  is  agreed  to  give  the  above  signification 

1  See  page  411. 


476  RESPIRATION. 

to  the  word  combustion ; l  but  this  must  simply  be  for  the 
purpose  of  retaining  the  name  applied  by  Lavoisier  to  the 
respiratory  process,  while  its  signification  is  altered  to  suit 
the  facts  which  have  since  taken  their  place  in  science.  There 
is  no  doubt  that  combustion  m  generally  regarded  as  signify- 
ing the  direct  and  active  union  of  oxygen  with  certain  prin- 
ciples, which  commonly  contain  carbon  and  hydrogen;  and 
the  immediate  products  of  this  union  are  carbonic  acid,  water, 
and  incidentally  heat  and  light.  It  is  certain  that  oxygen 
does  not  unite  in  the  body  directly  with  carbon  and  hydrogen, 
though  it  is  consumed,  and  carbonic  acid  and  water  are  pro- 
duced, in  respiration.  Important  intermediate  phenomena 
take  place,  and  we  do  not  therefore  fully  express  the  respiratory 
process  by  the  term  combustion.  The  researches  of  Spallan- 
zani,  W.  F.  Edwards,  Collard  de  Martigny, 2  and  others,  who 
have  demonstrated  the  abundant  exhalation  of  carbonic  acid 
by  animals  and  by  tissues  deprived  of  oxygen,  show  that  it 
is  not  a  product  of  combustion  of  any  of  the  principles  of  the 
organism.3 

Rejecting  this  hypothesis  as  insufficient  to  explain  the 
intimate  nature  of  the  respiratory  process,  it  remains  to  be 
seen  how  satisfactorily,  in  the  present  state  of  the  science,  it 
is  possible  to  answer  the  several  questions  proposed  at  the 
beginning  of  this  chapter. 

1.  In  what  way  is  the  oxygen  consumed  in  the  system  f — 
Oxygen,  first  taken  from  the  air  by  the  plasma  of  the  blood, 
is  immediately  absorbed  by,  and  enters  into  the  composition 
of,  the  red  corpuscles.  Part  of  the  oxygen  disappears  in  the 
red  corpuscles  themselves,  and  carbonic  acid  is  given  of£ 

1  LONGET,  Traite  de  Physiologie,  Paris,  1861,  tome  i.,  p.  392,  note. 

2  COLLARD  DE  MARTIGNY,  Recherches  Experimentales   et  Critiques  sur  V Ab- 
sorption et  sur  T Exhalation  Kcspiratoires. — Journal  de  Physiologie,   1830,  tome 
x.,  p.  111. 

3  Various  other  considerations  concerning  the  combustion  theory  of  respira- 
tion, such  as  the  so-called  "  respiratory,  or  calorific  food,"  will  be  discussed  in 
connection  with  the  subject  of  animal  heat. 


CONSUMPTION   OF   OXYGEN.  477 

To  how  great  an  extent  this  takes  place  it  is  impossible  to 
say ;  but  it  is  evident,  even  from  a  study  of  the  methods  of 
analyses  of  the  blood  for  gases,  that  the  property  of  absorbing 
oxygen  and  giving  off  carbonic  acid,  which  Spallanzani  dem- 
onstrated to  belong  to  the  tissues,  is  possessed  as  well  by  the 
red  corpuscles.  Daring  life  it  is  not  possible  to  determine 
how  far  this  takes  place  in  the  blood,  and  how  far  in  the 
tissues.  Lagrange  and  •  Hassenfratz *  advanced  the  theory 
that  all  the  respiratory  change  takes  place  in  the  blood  as  it 
circulates  ;  but  the  avidity  of  the  tissues  for  oxygen,  and  the 
readiness  with  which  they  exhale  carbonic  acid,  leave  no 
room  for  doubt  that  much  of  this  change  is  effected  in  their 
substance.  The  late  experiments  of  Bernard,8  showing  that 
when  blood  is  sent  to  the  glands  in  large  quantities,  the 
oxygen  is  only  imperfectly  destroyed,  the  blood  which  is 
returned  by  the  veins  having  nearly  the  color  of  arterial 
blood,  are  positive  evidence  against  this  view. 

Oxygen,  carried  by  the  blood  to  the  tissues,  is  appropri- 
ated and  consumed  in  their  substance,  together  with  the  nu- 
tritive materials  with  which  the  circulating  fluid  is  charged. 
We  are  acquainted  with  some  of  the  laws  which  regulate  its 
consumption,  but  have  not  been  able  to  follow  it  out  and  as- 
certain the  exact  nature  of  the  changes  which  take  place. 
Some  have  said  that  oxygen  unites  with  the  iron  of  the 
blood,  or  with  the  coloring  matter  of  the  corpuscles ;  but  ex- 
periments on  this  point  are  contradictory  and  unsatisfactory. 
Some  have  said  that  it  unites  with  the  hydro-carbons  of  the 
blood  and  of  the  tissues  ;  but  there  is  more  evidence  that  it 
enters  into  combination  chiefly  with  the  organic  nitrogenized 
principles.  All  that  we  can  say  definitely  on  this  point  is, 

1  HASSENFRATZ,  Memoire  sur  la  Combination  de  TOxygene  avec  le  Carbone  et 
r  Hydrogene  du  Sang,  sur  la  Dissolution  de  V  Oxgyene  dans  le  Sang,  et  sur  la  Maniere 
dont  le  Calorique  se  degage. — Annales  de  Chimie,  1791,  tome  ix.,  p.  261. 

2  Liquides  de  C  Organisme,  tome  i. ;  and  unpublished  lectures  at  the  College  of 
France,  1861.     In  the  latter,  Bernard  gives  comparative  analyses  of  the  venous 
blood  from  the  submaxillary  gland,  showing  a  larger  proportion  of  oxygen  during 
its  functional  activity  than  during  repose. 


478  RESPIRATION. 

that  it  unites  with  the  organic  principles  of  the  system,  satis- 
fying the  "  respiratory  sense,"  and  supplying  an  imperative 
want  which  is  felt  by  all  animals,  and  extends  to  all  parts  of 
the  organism.  After  being  absorbed,  it  is  lost  in  the  intri- 
cate processes  of  nutrition.  «There  is  no  evidence  in  favor  of 
the  view  that  oxygen  unites  directly-  with  carbonaceous  mat- 
ters in  the  blood  which  it  meets  in  the  lungs,  and,  by  direct 
union  with  carbon,  forms  carbonic  acid. 

2.  How  is  carbonic  acid  produced  ~by  the  system  f — 
That  carbonic  acid  makes  its  appearance  in  the  blood  it- 
self, produced  in  the  red  corpuscles,  has  been  abundantly 
proven  by  observations  already  cited;  though  it  is  impos- 
sible to  determine  to  what  extent  this  takes  place  during 
life.  It  is  likewise  a  product  of  the  physiological  decompo- 
sition of  the  tissues,  whence  it  is  absorbed  by  the  blood  cir- 
culating in  the  capillaries  and  conveyed  by  the  veins  to  the 
right  side  of  the  heart.  It  has  been  experimentally  demon- 
strated that  its  production  is  not  immediately  dependent 
upon  the  absorption  of  oxygen ;  for  it  will  go  on  in  an  atmos- 
phere of  hydrogen  or  of  nitrogen.  It  is  most  reasonable  to 
consider  the  carbonic  acid  thus  formed  as  a  product  of  excre- 
tion or  destructive  assimilation,  like  urea,  creatine,  or  choles- 
terine.  The  fact  that  it  may  easily  be  produced  artificially, 
out  of  the  body,  does  not  demonstrate  that  its  formation 
in  the  body  is  as  simple  as  when  it  is  formed  by  the  pro- 
cess of  combustion.  We  may  be  able  at  some  future  time 
to  produce  artificially  all  the  excrementitious  principles, 
as  has  already  been  done  in  the  case  of  urea ; 1  but  we  are 
hardly  justified  in  supposing  that  the  mode  of  formation 
of  this  principle,  as  one  of  the  phenomena  of  nutrition,  is 
precisely  the  same  as  when  it  is  made  by  our  chemical  ma- 
nipulations. 

1  Woller  first  formed  urea  artificially  by  a  union  of  cyanic  acid  and  am- 
monia. Since  then  it  has  been  prepared  by  chemists  by  various  processes 
(LEHMAKN,  Physiological  Chemistry,  Philadelphia,  1855,  vol.  i.,  p.  147). 


KESPIKATOKY    SENSE.  .  479 

As  expressing  nearly  all  that  is  known,  even  at  the  pres- 
ent day,  regarding  the  mode  of  formation  of  carbonic  acid 
in  the  economy,  we  may  take  the  following  concluding  passage 
from  the  paper  of  Collard  de  Martigny,  published  in  1830 : l 

"  The  carbonic  acid  expired  is  a  product  of  assimilative 
decomposition,  secreted  in  the  capillaries  and  excreted  by  the 
lungs." 

The  carbonic  acid  thus  produced  is  taken  up  by  the 
blood,  part  of  it  in  a  free  state  in  solution,  particularly  in 
the  plasma,  and  a  part  which  has  united  with  the  carbonates 
to  form  bicarbonates.  Carried  thus  to  the  lungs,  the  free 
gas  is  removed  by  simple  displacement,  and  that  which 
exists  in  combination  is  set  free  by  the  acids  found  in  the 
pulmonary  substance. 

3.  What  is  the  nature  of  the  intermediate  processes,  from 
the  disappearance  of  oxygen  to  the  evolution  of  carbonic 
acid  ? — A  definite  answer  to  this  question  would  complete 
our  knowledge  of  the  respiratory  process ;  but  this,  in  the 
present  state  of  the  science,  we  are  not  prepared  to  give.  "We 
can  only  repeat  what  has  already  been  so  frequently  referred 
to,  that  oxygen  must  be  considered  as  a  nutritive  principle, 
and  carbonic  acid  a  product  of  excretion.  The  intermediate 
processes  belong  to  the  general  function  of  nutrition,  with 
the  intimate  nature  of  which  we  are  unacquainted.  We 
have  not  sufficient  evidence  for  supposing  that  this  process 
is  identical  with  what  is  generally  known  as  combustion. 

The  Respiratory  Sense;  or  Want  on  the  part  of  the  System 
which  induces  the  Respiratory  Movements.  (Besoin  de 
Eespirer.) 

We  are  all  familiar  with  the  peculiar  and  distressing 

1  Loc.  cit.,  p.  160.  The  author  adds:  "The  chemical  theory  of  Lavoisier, 
of  respiration,  is  a  gratuitous  supposition.  This  function  should  be  considered 
as  a  complete  series  of  acts  of  general  assimilation." 


480  RESPIRATION. 

sense  of  suffocation  which  attends  an  interruption  in  the  re- 
spiratory process.  Under  ordinary  conditions,  the  act  of 
breathing  takes  place  without  our  knowledge;  but  even 
when  the  air  is  but  little  vitiated,  when  its  entrance  into  the 
lungs  is  slightly  interfered  dwith,  or  when  a  considerable 
portion  of  the  pulmonary  structure  is  involved  by  disease, 
we  experience  a  certain  sense  of  uneasiness,  and  become  con- 
scions  of  the  necessity  of  respiratory  efforts.  This  gradually 
merges  into  the  sense  of  suffocation,  and,  if  the  obstruction  be 
sufficient,  is  followed  by  convulsions,  insensibility,  and  final- 
ly by  death. 

Though  we  are  not  sensible  of  any  want  of  air  under  or- 
dinary conditions,  it  was  proven  by  the  celebrated  experi- 
ment of  Robert  Hook,  in  1664,  that  there  is  a  want  always 
felt  by  the  system ;  and  that  if  this  want  be  effectually  sup- 
plied, no  respiratory  movements  will  take  place.  We  have 
often  repeated  the  experiment  demonstrating  this  fact.  If  a 
dog  be  brought  completely  under  the  influence  of  ether,  the 
chest  and  abdomen  opened,  and  artificial  respiration  be 
carefully  kept  up  by  means  of  a  bellows  fixed  in  the  trachea, 
even  after  the  animal  has  come  from  under  the  influence  of 
the  anaesthetic,  so  as  to  look  around  and  wag  his  tail  when 
spoken  to,  he  will  frequently  cease  all  respiratory  move- 
ments when  the  air  is  properly  supplied  to  the  lungs.  This 
fact  can  be  very  satisfactorily  observed,  as  the  diaphragm 
and  other  important  respiratory  muscles  are  denuded,  and 
exposed  to  view.  If  the  artificial  respiration  be  interrupted 
or  imperfectly  performed,  the  animal  almost  immediately 
feels  the  want  of  air,  and  the  exposed  respiratory  muscles 
are  thrown  into  violent  but  ineffectual  contraction.1 

It  is  generally  admitted,  indeed,  that  there  exists  in  the 

1  For  full  details  of  these  experiments  the  reader  is  referred  to  an  article  by 
the  author,  entitled  Experimental  Researches  on  Points  connected  with  the  Action 
of  the  Heart  and  with  Respiration  (American  Journal  of  the  Medical  Sciences,  Oct., 
1861).  Since  the  publication  of  this  paper,  the  experiments  on  respiration  have 
been  frequently  repeated  publicly,  and  the  conclusions  verified. 


BESPIEATOKY   SENSE.  481 

system  what  may  appropriately  be  called  a  respiratory  sense, 
or,  as  it  is  called  by  the  French,  l>esoin  de  respirer,  which  is 
conveyed  to  the  respiratory  nervous  centre  and  gives  rise  to 
the  ordinary  reflex  and  involuntary  movements  of  respira- 
tion ;  that  this  sense  is  exaggerated  by  any  thing  which  inter- 
feres with  respiration,  and  is  then  carried  on  to  the  brain, 
where  it  is  appreciated  as  dyspnoea,  and  finally  as  the  over- 
powering sense  of  suffocation.  An  exaggeration  of  the 
respiratory  sense  constitutes  an  oppression,  which  is  referred 
to  the  lungs.  It  has  been  demonstrated,  however,  that  the 
sensation  of  hunger,  which  is  felt  in  the  stomach,  and  of 
thirst,  which  is  felt  in  the  throat  and  fauces,  have  their  seat 
really  in  the  general  system,  and  are  instinctively  referred 
to  the  parts  mentioned,  because  they  are  severally  relieved  by 
the  introduction  of  food  into  the  stomach,  and  the  passage 
of  liquid  along  the  throat  and  oesophagus.  It  cannot  there- 
fore be  assumed,  from  sensations  only,  that  the  sense  of  want 
of  air  is  really  located  in  the  lungs.  The  question  of  its  seat 
and  its  immediate  cause  is  one  of  the  most  interesting  of 
those  connected  with  respiration. 

Many  physiologists  accept  the  view  of  Marshall  Hall,  who 
first  accurately  described  the  reflex  phenomena,  that  the  re- 
spiratory sense  is  located  in  the  lungs,  is  carried  to  the  medulla 
oblongata  by  the  pulmonary  branches  of  the  pneumogastric 
nerves,  and  is  due  to  the  accumulation  of  carbonic  acid  in  the 
pulmonary  vesicles ;  but  there  are  facts  in  physiology  and 
pathology  which  are  inconsistent  with  such  an  exclusive  view. 

In  cases  of  disease  of  the  heart,  when  the  system  is  im- 
perfectly supplied  with  oxygenated  blood,  the  sense  of  suffoca- 
tion is  frequently  most?  distressing,  though  the  lungs  be  unaf- 
fected, and  receive  a  sufficient  supply  of  pure  air.  This  and 
other  similar  facts  led  Berard  to  adopt  the  view  that  the 
respiratory  sense  has  its  point  of  departure  in  the  right  cavi- 
ties of  the  heart,  and  is  due  to  their  disterition  as  the  result  of 
obstruction  to  the  passage  of  blood  through  the  lungs.1  John 

1  Cours  de  Physiologic,  tome  ili.,  p.  523. 
31 


482  RESPIRATION. 

Reid  thought  it  was  due  in  a  measure  to  the  circulation  of 
venous  blood  in  the  medulla  oblongata.1  "What  lias  been 
shown  to  be  the  correct  explanation  was  given  by  Yolkmann 
in  1841.  He  regarded  the  sense  of  want  of  air  as  dependent 
on  a  deficiency  of  oxygen  in  "the  tissues,  producing  an  im- 
pression which  is  conveyed  to  the  medulla  oblongata  bv  the 
nerves  of  general  sensibility.  By  a  series  of  experiments,  tin's 
observer  disproved  the  view  that  this  sense  resides  in  the  lungs 
and  is  transmitted  along  the  pneumogastric  nerves  ;  and  by 
exclusion,  he  located  it  in  the  general  system,  and  showed  that 
such  a  supposition  is  competent  to  explain  all  the  phenomena 
connected  with  the  respiratory  movements.8  In  the  hope  of 
settling  some  of  these  questions,  which  might  be  regarded  as 
somewhat  uncertain,  we  instituted,  a  few  years  ago,  a  series  of 
experiments,  which  were  embodied  in  the  paper  already  re- 
ferred to.3  In  these  observations,  the  following  facts,  some  of 
which  had  been  previously  noted,  were  demonstrated ;  and 
their  results  leave  no  doubt  as  to  the  location  and  cause  of 
the  respiratory  sense : 

1.  If  the  chest  be  opened  in  a  living  animal,  and  artificial 
respiration  be  carefully  performed,  inflating  the  lungs  suffi- 
ciently but  cautiously,  and  taking  care  to  change  the  air  in 

1  An  Experimental  Investigation  into  the  Functions  of  the  Eighth  Pair  of 
Nerves,  etc.  Part  second.  Anatomical  and  Physiological  Researches,  Edin- 
burgh, 1848,  p.  285  ;  and  Edinburgh  Medical  and  Surgical  Journal, 
April,  1839. 

3  YOLKMAXX,  in  Schmidt's  Jahrbucher,  1842,  p.  290.  Yolkmann  shows  that 
after  division  of  the  pneumogastrics,  an  animal  dies  when  deprived  of  air,  not 
calmly,  but  with  undoubted  symptoms  of  distress  from  suffocation,  as  if  it  had 
been  strangled  without  previous  division  of  the  vagi.  He  also  made  a  number  of 
experiments,  in  which  respiratory  efforts  continued,  for  many  minutes  after  extir- 
pation of  the  lungs,  in  cats  and  dogs,  care  being  taken  to  leave  the  phrenic  nerves 
intact.  He  goes  on  to  reason  that  the  sense  of  want  of  air  must  reside  in  the  gen- 
eral system,  that  it  is  due  to  a  deficiency  of  oxygen,  and  that  its  exaggeration 
constitutes  the  sense  of  suffocation.  His  observations  do  not  show,  however, 
that  this  is  not  due  to  the  presence  of  carbonic  acid,  as  has  been  supposed  by 
many.  Yierordt  is  of  the  opinion  that  the  respiratory  sense  is  due  to  the  circu- 
lation of  the  venous  blood  in  the  substance  of  the  nerves. 

*  American  Journal,  October,  1861. 


the  bellows  every  few  moments,  as  long  as  this  is  continued, 
the  aTiimail  wiQ  make  no  respiratory  effort  ;  showing  that,  for 
the  time,  the  respiratory  sense  is  abolished. 

2.  l^en  the  artifidal  respiration  is  m^ 

ratory  muscles  are  thrown  into  contraction,  and  the  animal 
makes  regular,  and  at  last  Tiolent  efforts.  If  we  now  expose 
an  artery,  and  note  the  color  of  the  blood  as  it  flows,  it  wfll 
be  observed  that  &e  respiratory  efforts  only  commence  when 
the  blood  in  the  vessel  begins  to  be  dark.  When  artificial 
respiration  is  resumed,  the  respiratory  efforts  cease  only  when 
the  blood  becomes  red  in  the  arteries.  The  invariable  result 
of  this  experiment  seems  to  show  that  the  respiratory  sense  is 
connected  with  a  supply  of  blood  containing  little  oxygen 
and  charged  with  carbonic  add  to  the  systemic  capillaries  by 
the  arteries,  and  that  it  varies  in  intensity  with  the  degree 
of  change  in  the  blood. 

3.  L£  while  artificial  respiration  is  regularly  performed,  a 
large  artery  be  opened,  and  the  system  be  thus  drained  of 
blood,  when  the  hemorrhage  has  proceeded  to  a  certain  ex- 
tent, the  animal  makes  respiratory  efforts,  which  become 
more  and  more  violent,  until  they  terminate,  just  before 
death,  in  general  convulsions.    The  s&me  result  follows  when 
the  blood  is  prevented  from  getting  to  the  system  by  applying 
a  ligature  to  the  aorta. 

These  facts,  which  may  be  successively  observed  in  a 
single  experiment,  remain  precisely  the  same  if  we  previously 
divide  both  pnemnogastrie  nerves  in  the  neck;  showing  that 
these  are  by  no  means  the  only  nerves  which  convey  the 
respiratory  sense  to  the  medulla  oblongata. 

The  conclusions  which  may  legitimately  be  drawn  from 
the  above-mentioned  facts  are  the  following : 

The  respiratory  sense  has  its  seat  in  the  system,  and  is 
transmitted  to  the  medulla  oblongata  by  the  general  sensory 
nerves.  It  is  not  located  in  the  lungs,  for  it  operates  when 
the  lungs  are  regularly  filled  with  pure  air,  if  the  system  be 
drained  of  the  oxygen-carrying  fluid. 


484:  RESPIRATION. 

It  is  due  to  a  want  of  oxygen  on  the  part  of  the  system, 
and  not  to  any  fancied  irritant  properties  of  carbonic  acid ; 
for  when  the  lungs  are  filled  with  air,  and  the  system  is  grad- 
ually drained  of  blood,  though  all  the  blood  which  finds  its 
way  to  the  capillaries  is  fullj  oxygenated,  as  the  quantity 
becomes  insufficient  to  supply  the  required  amount  of  oxygen, 
the  sense  of  want  of  air  is  felt,  and  respiratory  efforts  take 
place.  The  experimental  results  on  which  these  conclusions 
are  based  are  invariable,  and  have  been  demonstrated  re- 
peatedly ;  so  that  the  location  of  the  respiratory  sense  in  the 
general  system,  and  the  fact  that  it  is  an  expression  of  a  want 
of  oxygen,  seem  as  certain  as  that  oxygen  is  taken  up  by  the 
blood  from  the  lungs,  and  distributed  to  the  tissues  by  the 
arteries.  With  this  view  we  can  explain  all  the  .reflex  phe- 
nomena which  are  connected  with  the  respiratory  function.1 

The  supposition  of  Berard  that  the  respiratory  sense  is 
due  to  distention  of  the  right  cavities  of  the  heart  is  disproved 
by  the  simple  experiment  of  sudden  excision  of  this  organ. 
In  that  case,  as  the  system  is  drained  of  blood,  efforts  at 
respiration  invariably  take  place,  though  the  supply  of  air  to 
the  lungs  be  continued. 

Sense  of  Suffocation. — We  must  separate,  to  a  certain 
extent,  the  respiratory  sense  from  the  sense  of  distress  from 
want  of  air,  and  its  extreme  degree,  the  sense  of  suffocation. 
The  first  is  not  a  sensation,  but  an  impression  conveyed  to 
the  medulla  oblongata,  giving  rise  to  involuntary  reflex  move- 
ments. The  necessities  on  the  part  of  the  system  for  oxygen 
regulate  the  supply  of  air  to  the  lungs.  We  have  already 
seen  that  every  five  to  eight  respirations,  or  when  the  respi- 

1  There  are  many  phenomena  which  physiologists  found  it  impossible  to  ex- 
plain on  the  supposition  that  the  "  besoin  de  respirer"  was  located  in  the  lungs  and 
conveyed  to  the  medulla  oblongata  by  the  pneumogastrics ;  among  which  may 
be  mentioned  the  effect  of  irritation  of  the  general  surface  in  the  resuscitation  of 
new-born  children  in  which  respiration  is  not  established  spontaneously.  Dr. 
Marshall  Hall  and  John  Keid  thought  that  in  these  cases  the  sensory  filaments  dis- 
tributed on  the  skin  had  something  to  do  in  transmitting  impressions  to  the  respi- 
ratory centre. 


SENSE   OF   SUFFOCATION.  485 

ratory  movements  are  a  little  restricted  under  the  influence 
of  depressing  emotions,  an  involuntary  deep  or  sighing  in- 
spiration is  made,  for  the  purpose  of  changing  the  air  in  the 
lungs  more  completely.  The  increased  consumption  of  oxygen 
and  a  certain  amount  of  interference  with  the  mechanical 
process  of  respiration  during  violent  muscular  exercise  put 
us  "  out  of  breath ;"  and  for  a  time  the  respiratory  move- 
ments are  exaggerated.  This  is  perhaps  the  first  physiological 
way  in  which  the  want  of  air  is  appreciated  by  the  senses. 
A  deficiency  in  hematosis,  either  from  a  vitiated  atmosphere, 
mechanical  obstruction  in  the  air-passages,  or  grave  trouble 
in  the  general  circulation,  produces  all  grades  of  sensations, 
from  the  slight  oppression  which  is  felt  in  a  crowded  room, 
to  the  intense  distress  of  suffocation.  When  hematosis  is  but 
slightly  interfered  with,  only  an  indefinite  sense  of  oppression 
is  experienced ;  the  respiratory  movements  are  a  little  in- 
creased, the  most  marked  effect  being  an  increase  in  the 
number  and  extent  of  sighing  inspirations.  In  the  experi- 
ments upon  animals  to  which  we  have  referred,  when  artifi- 
cial respiration  was  interrupted,  we  first  noticed  regular  and 
not  violent  contractions  of  the  respiratory  muscles ;  but  as  the 
sense  of  want  of  air  increased,  every  muscle  which  could  be 
used  to  raise  the  chest  was  brought  into  action.  In  the 
human  subject  in  this  condition,  the  countenance  has  a 
peculiar  expression  of  anxiety  and  distress,  and  the  move- 
ments soon  extend  to  the  entire  muscular  system,  resulting 
in  general  convulsions,  and,  finally,  insensibility. 

Bearing  in  mind  the  fact,  that  though  these  sensations 
are  referred  to  the  lungs,  indicating  increased  respiratory 
effort  as  the  common  means  for  their  relief,  they  have  their 
real  point  of  departure  in  the  general  system,  we  can  under- 
stand the  operation  of  various  abnormal  conditions  of  the 
circulation,  when  the  lungs  are  adequately  supplied  with 
fresh  air.  The  first  subjective  symptom  of  air  in  the  veins 
is  a  sense  of  impending  suffocation.  There  is  no  want  of  air 
in  the  lungs,  but  the  circulation  is  instantaneously  inter- 


486  RESPIRATION. 

rupted,  and  oxygenated  blood  is  not  supplied  to  the  tis- 
sues. The  same  effect,  practically,  follows  abstraction  of 
the  circulating  fluid,  or  the  absorption  of  any  poisonous  agent 
which  destroys  the  function  of  the  corpuscles  as  carriers  of 
oxygen ;  though  in  hemorrhage,  the  effects  are  not  as  marked, 
as  generally  the  system  is  gradually  debilitated  by  the  pro- 
gressive loss  of  blood.  It  was  invariably  noticed  in  the  ex- 
periments above  referred  to,  that  after  the  division  of  a  large 
artery,  though  artificial  respiration  was  carefully  performed, 
respiratory  efforts  took  place  when  the  system  was  nearly 
drained  of  blood.  As  the  hemorrage  continued,  these  efforts 
became  more  violent,  and  eventuated,  just  before  death,  in 
general  convulsions.1  A  comparison  of  this  experiment  with 
those  in  which  artificial  respiration  was  simply  interrupted 
shows  that  in  sudden  hemorrhage  there  can  be  no  doubt  that 
the  system  feels  the  want  of  oxygen ;  and  when  the  loss  of 
blood  is  very  great,  this  is  increased  until  it  amounts  to  a 
sense  of  suffocation.  In  gradual  hemorrhage,  there  is  a  con- 

1  "Expt.  xxxiv.,  Feb.  19,  1861.  A  good-sized  dog  was  etherized  and  the  chest 
opened  in  the  usual  way.  Artificial  respiration  was  established,  and  Expt.  xxix. 
verified.  The  blood  was  then  allowed  to  flow  freely  from  the  femoral  artery, 
while  artificial  respiration  was  actively  continued.  While  the  blood  continued  to 
flow,  the  respiratory  muscles  were  carefully  observed.  During  the  first  part  of 
the  bleeding  no  respiratory  efforts  took  place ;  but  when  the  blood  had  flowed  for 
a  considerable  time,  and  the  system  was  becoming  drained,  respiratory  efforts  com- 
menced, feeble  at  first,  but  as  the  bleeding  continued,  becoming  more  violent  until  the 
whole  muscular  system  was  affected  by  convulsive  movements"  (Am.  Journ.,  loc. 
cit.,  p.  376.) 

Convulsions  after  profuse  hemorrhage  have  long  been  observed  by  physiol- 
ogists, but  no  entirely  satisfactory  explanation  of  their  occurrence  has  ever  been 
given.  There  now  can  be  no  doubt  that  they  are  due  to  a  deficiency  of  oxygen. 
The  experiments  of  Kusmaul  and  Tenner  (  On  the  Nature  and  Origin  of  Epilepti- 
form  Convulsions  caused  by  Profuse  Bleeding.  New  Sydenham  Society,  London, 
1859)  show  that  convulsions  may  be  produced  by  ligature  of  the  great  vessels 
carrying  blood  to  the  brain.  In  this  case  they  are  probably  due  to  a  deficiency  of 
oxygen  in  this  vascular  and  highly  organized  part.  In  their  experiments,  which 
were  made  on  rabbits,  it  was  observed  that  "  respiration  is  at  first  accelerated,  but 
shortly  afterwards,  a  little  while  before  the  approach  of  general  convulsions,  it 
becomes  prolonged  and  deep."  P.  14. 


KESPIRATOKY   EFFOKTS   BEFORE   BIRTH.  487 

servative  provision  of  Nature,  by  which  faintness  and  dimi- 
nution in  the  force  of  the  heart's  action  favor  the  arrest  of 
the  flow  of  blood. 

Poisoning  by  carbonic  oxide  is  generally  accompanied  with 
convulsions,  which  arise  from  the  sense  of  suffocation,  and  are 
due  to  a  fixation  of  this  gas  in  the  blood-corpuscles,  by  which 
they  are  rendered  incapable  of  giving  oxygen  to  the  system. 
Convulsions  also  attend  poisoning  by  hydrocyanic  acid,  in 
cases  in  which  the  system  is  not  overpowered  immediately  by  a 
large  dose  of  this  agent,  and  the  muscular  irritability  destroyed. 

Experiments  have  failed  to  show  that  the  respiratory 
sense,  or  the  sense  of  suffocation,  is  due  to  irritation  produced 
by  carbonic  acid  in  the  non-oxygenated  blood. 

Respiratory  Efforts  ~before  Birth. 

It  is  generally  admitted  that  one  of  the  most  important 
functions  of  the  placenta,  and  the  one  which  is  most  im- 
mediately connected  with  the  life  of  the  foetus,  is  a  respira- 
tory interchange  of  gases,  analogous  to  that  which  takes 
place  in  the  gills  of  aquatic  animals.  The  vascular  pro- 
longations from  the  foetus  are  continually  bathed  in  the 
blood  of  the  mother,  and  this  is  the  only  way  in  which  it 
can  receive  oxygen.  Notwithstanding  the  statements  of 
those  who  have  been  unable  to  note  any  difference  in  color 
between  the  blood  contained  in  the  umbilical  arteries  and 
the  vein,  there  are  direct  observations  showing  that  such  a 
difference  does  exist.  Legallois  frequently  observed  a  bright 
red  color  in  the  blood  of  the  umbilical  vein ;  and  on  alter- 
nately compressing  and  releasing  the  vessel,  he  saw  the  blood 
change  in  color  successively  from  red  to  dark,  and  dark  to 
red.1  As  oxygen  is  thus  adequately  supplied  to  the  system, 
the  foetus  is  in  a  condition  similar  to  that  of  the  animals  in 
which  artificial  respiration  was  effectually  performed.  The 
want  of  oxygen  is  fully  met,  and  therefore  no  respiratory 

1  BERARD,  Cours  de  Physiologic,  tome  iii.,  p.  422. 


4:88  RESPIRATION. 

efforts  take  place.  Respiratory  movements  will  take  place, 
however,  even  in  very  young  animals,  when  there  is  a  defi- 
ciency of  oxygen  in  the  system.  It  has  been  observed  that 
the  liquor  amuii  occasionally  finds  its  way  into  the  respira- 
tory passages  of  the  foetus,  whose  it  could  only  enter  in  efforts 
at  respiration.  "Winslow,  in  the  latter  part  of  the  last  cen- 
tury, first  noticed  respiratory  efforts  in  the  foetuses  of  cats 
and  dogs,  in  the  uterus  of  the  mother  during  life ; 1  and  many 
others  have  observed  that  when  foetuses  are  removed  from 
vascular  connection  with  the  mother,  they  will  make  vigor- 
ous efforts  at  respiration.  This  fact  we  have  frequently  had 
occasion  to  demonstrate  in  making  operations  upon  pregnant 
animals.  After  the  'death  of  the  mother,  the  foetus  always 
makes  a  certain  number  of  respiratory  efforts,  which  are  not 
uncertain  in  their  character,  but  distinct,  accompanied  by 
great  elevation  of  the  ribs,  opening  of  the  mouth,  and  follow- 
ing each  other  at  regular  intervals,  independently  of  irritation 
of  the  general  surface.11 

From  what  has  been  experimentally  demonstrated  with 
regard  to  the  location  and  cause  of  the  respiratory  sense  after 
birth,  it  is  evident  that  want  of  oxygen  is  the  cause  of  re- 
spiratory movements  in  the  foetus.  When  the  circulation  in 
the  maternal  portion  of  the  placenta  is  interrupted  from  any 
cause,  or  when  the  blood  of  the  foetus  is  obstructed  in  its 
course  to  and  from  the  placenta,  the  impression  due  to  the 
want  of  oxygen  is  conveyed  to  the  medulla  oblongata,  and 
efforts  at  respiration  are  the  result.  This  cannot  be  due  to 
an  accumulation  of  carbonic  acid  in  the  lungs,  and  is  entirely 

1  British  and  Foreign  Medico- Chirurgical  Review,  April,  1864,  p.  330. 

2  We  take  from  our  note-book  the  following  observation  showing  respiratory 
efforts  in  a  very  young  animal : 

"  Jan.  6,  1865.  In  operating  to-day  on  a  small-sized  bitch,  for  the  purpose  of 
demonstrating  the  glycogenic  process  in  the  liver,  I  found  her  pregnant,  and  hi 
the  uterus  were  six  pups,  certainly  not  more  than  one-fourth  the  size  which  they 
attain  before  birth.  (They  were  four  niches  long.)  On  removing  them  from  the 
womb,  and  dividing  the  umbilical  vessels,  they  all  made  a  number  of  profound 
respiratory  efforts  at  intervals  of  from  two  to  three  minutes." 


CUTANEOUS   EESPIEATION.  489 

consistent  with  our  views,  locating  the  respiratory  sense  in 
the  general  system.1 

Cutaneous  Respiration. 

This  mode  of  respiration,  though  very  important  in 
many  of  the  lower  orders  of  animals,  is  insignificant  in  the 
human  subject,  and  even  more  slight  in  animals  covered 
with  hair  or  feathers.2  Still,  an  appreciable  quantity  of 
oxygen  is  absorbed  by  the  skin  of  the  human  subject, 
and  an  amount  of  carbonic  acid,  which  is  proportionately 
larger,  is  exhaled.  Exhalation  of  carbonic  acid,  which  is 
connected  rather  with  the  functions  of  the  skin  as  a  general 
excreting  organ  and  is  by  no  means  an  essential  part  of  the 
respiratory  process,  will  be  more  fully  considered  under  the 
head  of  excretion.  Carbonic  acid  is  given  off  with  the  general 
emanations  from  the  surface,  being  found  at  the  same  time 
in  solution  in  the  urine  and  in  most  of  the  secretions.  It  is 
well  known  that  death  follows  the  application  of  an  imper- 
meable coating  to  the  entire  cutaneous  surface;  but  this  is 
by  no  means  due  to  a  suppression  of  its  respiratory  function 
alone.  The  skin  has  other  offices,  particularly  in  connection 
with  regulation  of  the  animal  temperature,  which  are  infi- 
nitely more  important. 

An  estimate  of  the  extent  of  cutaneous,  compared  with 
pulmonary  respiration,  has  been  made  by  Scharling,3  by  com- 

1  The  physiological  and  pathological  questions  connected  with  the  subject  of 
"  respiration  before  birth,"  are  ably  and  exhaustively  discussed  in  a  review  pub- 
lished in  the '  Medico- CMrurgical  Review,  for  April,  1864.     A  number  of  ex- 
periments by  various  observers  are  here  detailed,  fully  establishing  the  facts  we 
have  stated.     Among  the  most  interesting  are  those  of  Schwartz,  showing  respi- 
ratory movements  in  foetuses,  when  care  was  taken  not  to  expose  them  to  the 
cool  air  or  any  other  irritation  of  the  general  surface,  p.  333. 

2  REGNAULT  and  REISET  found  the  cutaneous  respiration  so  slight  in  the  ani- 
mals which  they  used  for  their  experiments,  that  its  influence  upon  the  compo- 
sition of  the  air  in  which  they  Were  confined  could  be  disregarded.     (Op.  cit.} 

3  In  MILNE-EDWARDS,  Lemons  sur  la  Phijsiologie,  tome  ii.,  p.  635.     The  reader 
will  here  find  an  account  of  the  experiments  of  DeMilly,  Abernethy,  and  others, 
demonstrating  the  absorption  of  oxygen  and  exhalation  of  carbonic  acid  by  the  skin. 


490  RESPIRATION. 

paring  the  relative  quantities  of  carbonic  acid  exhaled  in  the 
twenty-four  hours.  According  to  this  observer,  the  skin 
performs  from  -fa  to  -fa  of  the  respiratory  function. 

Asphyxia. 

The  effects  of  cutting  off  the  supply  of  oxygen  from  the 
lungs  are  mainly  referable  to  the  circulatory  system,  and 
have  already  been  considered  under  the  head  of  the  influence 
of  respiration  upon  the  circulation.1  It  will  be  remembered 
that  in  asphyxia  the  non-aerated  blood  passes  with  so  much 
difficulty  through  the  systemic  capillaries,  as  finally  to  arrest 
the  action  of  the  heart.  It  is  the  experience  of  those  who 
have  experimented  on  this  subject,  that  the  movements  of 
the  heart,  once  arrested  in  this  way,  cannot  be  restored ;  but 
that  while  the  slightest  regular  movements  continue,  its 
functions  will  gradually  return  if  air  be  readmitted  to  the 
lungs. 

A  remarkable  power  of  resisting  asphyxia  exists  in  newly 
born  animals  that  have  never  breathed.  This  was  noticed  by 
Haller  and  others,  and  has  been  the  subject  of  numerous 
experiments,  among  which  we  may  mention  those  of  Buffon, 
Legallois,  and  W.  F,  Edwards.  Legallois  found  that  young 
rabbits  would  live  for  fifteen  minntes  deprived  of  air  by 
submersion,  but  that  this  power  of  resistance  diminished 
rapidly  with  age.2  W.  F.  Edwards  has  shown  that  there 
exists  a  great  difference  in  this  regard  in  different  classes  of 
animals.  Dogs  and  cats,  that  are  born  with  the  eyes  shut,  and 
in  which  there  is  at  first  a  very  slight  development  of  animal 
heat,  will  show  signs  of  life  after  submersion  for  more  than 
half  an  hour;  while  Guinea  pigs,  which  are  born  with  the  eyes 
open,  are  much  more  active,  and  produce  a  greater  amount 
of  heat,  will  not  live  more  than  seven  minutes.3 

1  See  page  290.  a  See  page  421,  note. 

8  W.  F.  EDWARDS,  De  V Influence  des  Agcns  Physiques  sur  la  Vie,  Paris,  1824, 
pp.  171,  172. 


ASPHYXIA.  491 

The  cause  of  this  peculiarity  has  been  attributed  to  the 
existence  of  the  foramen  ovale,  enabling  the  blood  to  get 
to  the  system  without  passing  through  the  lungs,  by  those 
who  regard  the  arrest  of  the  circulation  in  asphyxia  as  due 
to  obstruction  to  the  pulmonary  circulation ;  but  this  expla- 
nation is  not  sufficient,  as  blood  passes  easily  through  the 
lungs  in  asphyxia,  and  is  obstructed  only  in  the  systemic 
capillaries. 

The  true  explanation  seems  to  be,  that  in  most  warm- 
blooded animals,  during  the  very  first  periods  of  extra-uterine 
life,  the  demands  on  the  part  of  the  system  for  oxygen  are 
comparatively  light.  At  this  time  there  is  very  little  activity 
in  the  processes  of  nutrition,  and  the  actual  consumption  of 
oxygen  and  exhalation  of  carbonic  acid  are  very  much  below, 
the  regular  standard  in  animals  of  this  class.  -In  fact,  their 
condition  is  somewhat  like  that  of  cold-blooded  animals.  The 
actual  difference  in  the  consumption  of  oxygen  immediately 
after  birth  and  at  the  age  of  a  few  days  is  sufficient  to  explain 
the  remarkable  power  of  resisting  asphyxia  just  after  birth. 
The  comparative  observations  of  Edwards  on  dogs,  cats,  and 
Guinea  pigs,  show  that  this  power  bears  a  definite  relation 
to  the  respiratory  activity. 

One  of  the  most  interesting  questions,  in  a  practical  point 
of  view,  connected  with  the  subject  of  asphyxia,  is  the  effect  on 
the  system  of  air  vitiated  from  breathing  in  a  confined  space. 
There  are  here  several  points  presented  for  consideration. 
The  effect  of  respiration  on  the  air  is  to  take  away  a  certain 
proportion  of  oxygen,  and  add  certain  principles  which  are 
regarded  as  deleterious.  The  emanation  which  is  generally 
regarded  as  having  the  most  decided  influence  upon  the 
system  is  carbonic  acid. 

A  careful  review  of  the  most  reliable  observations  on  this 
subject  shows  that  the  influence  of  carbonic  acid  is  generally 
very  much  over-estimated.  In  poisoning  by  charcoal  fumes, 
it  is  generally  carbonic  oxide  which  is  the  active  princi- 


492  RESPIRATION. 

pie.  Kegnault  and  Eeiset1  exposed  dogs  and  rabbits  for 
many  hours  to  an  atmosphere  containing  23  parts  per  100  of 
carbonic  acid  artificially  introduced,  and  30  to  40  parts  of 
oxygen,  without  any  ill  effects.  They  took  care,  however, 
to  keep  up  a  constant  supply  ef  oxygen.  These  experiments 
are  at  variance  with  the  results  obtained  by  others,  but  Re- 
gnault  and  Reiset  explain  this  difference  by  the  supposition 
that  the  gases  in  other  observations  were  probably  impure, 
containing  a  little  chlorine  or  carbonic  oxide.  There  is  no 
reason  to  doubt,  from  the  high  reputation  of  the  observers 
for  skill  and  accuracy,  that  their  experiments  are  perfectly 
reliable ;  and  in  that  case,  they  prove  that  carbonic  acid  does 
not  act  upon  the  system  as  a  poison.  This  view  is  sustained 
by  the  more  recent  observations  of  Dr.  Hammond,  which  we 
give  in  his  own  words : 

"  I  confined  a  sparrow  under  a  large  bell-glass,  having 
two  openings.  Through  one  of  these  I  introduced  every 
hour  1,000  cubic  inches  of  an  atmosphere  containing  45  parts 
of  oxygen,  30  of  nitrogen,  and  25  of  carbonic  acid,  allowing 
the  vitiated  air  in  which  the  animal  had  respired  partially  to 
escape.  At  the  end  of  twelve  hours  the  bird  was  in  as  good 
a  condition  as  at  the  commencement  of  the  experiment ;  and 
when  the  bell-glass  was  raised,  it  flew  away  as  if  nothing  had 
happened  to  it.  A  mouse  subjected  to  a  similar  experiment 
also  suffered  no  inconvenience." 2 

In  breathing  in  a  confined  space,  the  distress  and  finally 
fatal  results  are  produced,  in  all  probability,  more  from  animal 
emanations  and  deficiency  of  oxygen,  than  from  the  presence 
of  carbonic  acid.  When  the  latter  gas  is  removed  as  fast  as 
it  is  produced,  the  effects  of  diminution  in  the  proportion  of 
oxygen  are  soon  very  marked,  and  progressively  increase  till 
death  occurs.  Bernard  has  shown  that  birds  enclosed  in  a 
confined  space,  from  which  the  carbonic  acid  is  carefully 

1  Loc.  dt. 

3  HAMMOND,  Treatise  on  Hygiene,  Philadelphia,  18G3,  p.  351. 


ASPHYXIA.  493 

removed,  will  gradually  consume  oxygen,  until,  when  death 
occurs,  the  proportion  is  reduced  to  from  3  to  5  parts  per 
100.1  When  the  carbonic  acid  is  allowed  to  remain,  the 
increased  density  of  the  atmosphere  interferes  with  the  dif- 
fusion between  the  gases  of  the  blood  and  the  air,  and  death 
supervenes  with  greater  rapidity. 

The  influence  on  animals  of  emanations  from  the  lungs 
and  general  surface,  from  which  the  carbonic  acid  and  watery 
vapor  have  been  removed,  has  been  shown  by  Dr.  Hammond 
to  be  very  decided  and  rapid.  He  confined  a  mouse  in  a 
large  glass  jar,  so  arranged  as  to  admit  fresh  air  as  the  at- 
mosphere became  rarefied  by  respiration,  causing  the  carbonic 
acid  to  be  absorbed  by  sponges  saturated  with  baryta-water, 
and  the  watery  vapor  by  pieces  of  chloride  of  calcium.  The 
animal  died  in  forty-five  minutes ;  when,  by  passing  the  gas- 
eous contents  of  the  jar  through  baryta-water,  it  was  shown 
to  contain  no  carbonic  acid,  and  the  presence  of  organic 
matter  in  large  quantity  was  demonstrated.2 

In  crowded  assemblages,  the  slight  diminution  of 
oxygen,  the  elevation  of  temperature,  increase  in  moisture, 
and  particularly  the  presence  of  organic  emanations,  com- 
bine to  produce  unpleasant  sensations.  The  terrible  ef- 
fects of  this  carried  to  an  extreme  were  exemplified  in  the 
confinement  of  the  146  English  prisoners,  for  eight  hours 
only,  in  the  "Black  Hole"  of  Calcutta;  a  chamber  eigh- 
teen feet  square,  with  only  two  small  windows,  and  those 
obstructed  by  a  verandah.  Out  of  this  number,  96  died  in 
six  hours,  and  123  at  the  end  of  the  eight  hours.  Many  of 

1  BERNARD,  Lemons  sur  les  Effets  des  Substances  Toxigues  et  Medicamenteuses, 
Paris,  1857,  p.  116. 

3  Op.  cit.,  p.  170.  "  For  the  detection  of  organic  matter  in  the  atmosphere, 
the  permanganate  of  potassa  affords  a  very  sensitive  reagent.  A  solution  of  this 
substance  in  water  loses  its  brilliant  red  color,  and  the  salt  undergoes  decompo- 
sition, when  air  containing  organic  matter  is  passed  through  it.  By  the  extent  to 
which  the  loss  of  color  reaches  we  are  enabled  to  form  an  approximative  idea  of 
the  amount  of  such  matter  present  in  the  air.  The  solution  is  placed  in  Liebig's 
bulbs,  and  the  air  is  drawn  through  it  by  means  of  an  aspirator."  P.  172. 


494:  RESPIRATION. 

those  who  immediately  survived  afterwards  died  of  putrid 
fever.1  This  frightful  tragedy  has  frequently  been  repeated 
on  emigrant  and  slave  ships,  by  confining  great  numbers  in 
the  hold  of  the  vessel,  where  they  were  entirely  shut  out  from 
the  fresh  air.  This  subject  possesses  great  pathological  in- 
terest; the  effects  of  an  insufficient  supply  of  air  and  the 
accumulation  in  the  atmosphere  of  animal  emanations  being 
very  important  in  connection  with  the  cause  and  prevention 
of  many  diseases. 

The  condition  of  the  system  has  a  marked  and  important 
influence  on  the  rapidity  with  which  the  effects  of  vitiated 
atmosphere  are  manifested,  as  we  should  anticipate  from  what 
we  know  of  the  variations  in  the  consumption  of  oxygen  under 
different  conditions.  As  a  rule,  the  immediate  effects  of  con- 
fined air  are  not  as  rapidly  manifested  in  weak  and  debilitated 
persons,  as  in  those  who  are  active  and  powerful.  It  has 
sometimes  b.een  observed,  in  cases  where  a  male  and  a  female 
have  attempted  suicide  together  by  the  fumes  of  charcoal, 
that  the  female  may  be  restored  some  time  after  life  is  ex- 
tinct in  the  male.  This  is  probably  owing  to  the  greater 
demand  for  oxygen  on  the  part  of  the  male. 

The  following  interesting  fact  is  reported  by  Bernard, 
showing  the  relative  power  of  resisting  asphyxia  in  health 
and  disease : 

"  Two  young  persons  were  in  a  chamber  warmed  by  a 
stove  fed  with  coke.  One  of  them  was  seized  with  asphyxia 
and  fell  unconscious.  The  other,  at  that  time  suffering  with 
typhoid  fever  and  confined  to  the  bed,  resisted  sufficiently  to 
be  able  to  call  for  help.  "We  know  already  that  this  resistance 
to  toxic  influences  is  manifested  in  animals,  when  they  are 
made  sick ;  we  here  have  the  proof  of  the  same  phenomenon 
in  man.  As  for  the  one  who,  in  good  health,  had  experienced 
the  effects  of  the  commencement  of  poisoning,  she  had  a 


1  A  full  account  of  the  sufferings  of  these  unfortunate  men,  by  one  of  the 
survivors,  is  to  be  found  in  the  Annual  Register,  1758,  p.  278. 


ASPHYXIA.  495 

paralysis  of  the  left  arm,  which  was  not  completely  cured  at 
the  end  of  six  months." 1 

It  is  thought  that  the  condition  of  syncope  has  an  influence 
on  the  power  of  resistance  to  asphyxia.  A  case  is  quoted  by 
Carpenter  in  which  a  woman,  who  had  been  submerged  for 
fifteen  minutes,  was  taken  out  of  the  water  and  recovered 
spontaneously.  She  stated  that  she  was  insensible  at  the 
moment  of  her  submersion.2 

When  poisoning  by  confined  air  is  gradual,  the  system 
becomes  somewhat  accustomed  to  the  toxic  influence ;  the 
temperature  of  the  body  is  lowered,3  and  an  animal  will  live 
in  an  atmosphere  which  will  produce  instantaneous  death  in 
one  that  is  fresh  and  vigorous.  Bernard  has  made  a  number 
of  curious  and  instructive  experiments  on  this  point.  In  one 
of  them,  a  sparrow  was  confined  under  a  bell-glass  for  one 
hour  and  a  half,  at  the  end  of  which  time  another  was  intro- 
duced, the  first  being  still  quite  vigorous.  The  second  be- 
came instantly  much  distressed,  and  died  in  five  minutes ; 
but  ten  minutes  after,  the  sparrow  which  had  been  confined 
for  more  than  an  hour  and  a.  half  was  released,  and  flew 
away.4 

This  is  simply  demonstrating,  with  experimental  accuracy, 
a  fact  of  which  we  are  all  conscious ;  for  it  is  well  known, 
that  going  from  the  fresh  air  into  a  close  room,  we  experience 
a  malaise  which  is  not  felt  by  those  who  have  been  in  the 
room,  for  a  length  of  time,  and  whose  emanations  have 
vitiated  the  atmosphere. 

1  BERNARD,  op.  ciL,  p.  197. 

2  CARPENTER,  Principles  of  Human  Physiology,  Am.  edit.,  1853,  p.  536. 

3  Bernard  noted  a  diminution  in  the  temperature  in  the  rectum  of  a  pigeon, 
from  105°  to  88°  Fahr.,  after  four  hours'  sojourn  in  a  confined  space,  containing 
732  cubic  inches  of  air.     The  animal  was  nearly  dead  when  removed.    (Loc.  cit. 
p.  128.) 

4  Op.  cit.,  p.  119. 


E  X. 


Air,  diffusion  of,  in  the  lungs, . . .  406 

composition  of, 413 

changes  of,  in  passage  through 

the  lungs, 423 

increase  in  temperature  of,  in 

passage  through  the  lungs, 423 

Air-cells,  anatomy  of, 362 

Albumen,  situations  and  quantity 

of, 81 

mode  of  extraction  and  prop- 
erties of, 82 

influence    of,    on    polarized 

light, 83 

tests  for, 83 

origin  and  functions  of, 83 

Albumiuometer, 84 

Albuminose, 85 

Alcohol,    exhalation    of,    by    the 

lungs, * 450 

Ammonia,  exhalation  of,  in  respi- 
ration,    448 

Arteries,  circulation  in, 240 

physiological  anatomy  of,.. .  241 

divisions  of, 243 

coats  of, 243 

nerves  in  walls  of, 245 

blood-vessels  in  walls  of, ...  245 

elasticity  of, 246 

experiments  showing  dilata- 
tion of, 247 

influence  of  elasticity  of,  on 

the  current  of  blood, 248 

contractility  of, 230 

locomotion  of,  and  produc- 
tion of  the  pulse, 252 

variations  in   caliber  of,    at 

different  periods  of  the  day, 261 

32 


Arterial  pressure, 261 

in  different  vessels, 206 

influence  of  respiration  on,. .  267 

influence  of  hemorrhage  on, .   269 

Arterial  circulation,  rapidity  of,. .  270 

apparatus  of  Volkmann  and 

Hiittenheim  for  measuring  ra- 
pidity of, 271 

apparatus  of  Vierordt, 272 

apparatus  of  Chauveau, 273 

rapidity  of,  in  different  ves- 
sels,    274 

Arterial  murmurs, 276 

Asphyxia, 490 

power  of  resistance  to  in  the 

newly-born, 421,  490 

from  breathing  in  a  confined 

space, 491,  495 

from  charcoal  fumes, 491 

influence  of,  on  pulmonary 

circulation, 343 

Besoin  de  respirer, 479-484 

Bicarbonate  of  soda, 45 

Biliverdine, 93 

Black  Hole  of  Calcutta, 493 

Blood,  general  considerations,. ...     95 

immediate     importance     to 

life, 96 

experiment  of  withdrawing  a 

large  quantity  from  the  vessels,     97 

transfusion  of, 97 

transfusion  of,  in  disease, ...     98 

transfusion    of,    in    experi- 
ments on  animals, !j9 

entire    quantity  of,  in    the 

body, 100 


498 


INDEX. 


Blood,  reaction,  odor,  and  opacity 
of, 104 

temperature  and  specific  gra- 
vity of, 105 

'color  of, 106 

color    of,   in    veins   of    the 

glands, 107 

analyses  of, 127 

inorganic  constituents  of,.. ..  128 

organic  nitrogenized  constit- 
uents of, 129 

organic  non-nitrogenized  con- 
stituents of, 129 

quantitative  analyses  of, 130 

quantitative  analysis  of,   by 

method  of  Becquerel  and  Ro- 

dier, 131 

quantitative   analysis  of,  by 

the  author's  method, 134 

table  of  composition  of, ....  138 

coagulation  of, 142 

rapidity  of  coagulation  of, . .   143 

circumstances  modifying  co- 
agulation of, 149 

coagulation  of,  in  the  organ- 
ism,  160 

office  of  coagulation  in  arrest 

of  hemorrhage, 153 

cause  of  coagulation  of, ....  156 

summary  of  properties  and 

functions  of, 167 

changes  of,  in  respiration, . .  452 

difference  in  color  between 

venous  and  arterial, 454 

general  differences  between 

arterial  and  venous, 470 

analyses  of,  for  gases, . .  458-464 

condition  of  gases  in, 466 

Blood-corpuscles  (red), 108 

anatomical  characters  of, ...  109 

table  of  measurements  of, ..   113 

chemical  characters  of, 117 

development  of, 118 

functions  of, 120 

(white), 121 

elementary  corpuscles, 126 

absorption  of  oxygen  by, ...  455 

Blood-crystals, 117 

Breathing  capacity,  extreme, 403 

Bronchial  tubes,  anatomy  of,. ...  360 

Calorific  elements, 60 

Capillaries,  circulation  in, 278 

anatomy  of, 279 

distribution  of, 281 

course  of  blood  in, 283 

Capillary  system,  capacity  of, 282 


Capillary  circulation,  microscopic 

examination  of, 284 

rapidity  of, 289 

relations  of,  to  respiration,. .   290 

causes  of, 293 

phenomena  in  patients  dead 

,     with  yellow  fever, 295 

influence  of  temperature  on,  297 

influence  of  direct  irritation 

on, 298 

Carbonate  of  lime, 42 

crystals  of,  in  internal  ear,. .     43 

formation  of,  in  analysis  by 

incineration, 43 

quantity  of  (table),  and  func- 
tion,      43 

Carbonate  of   soda,   quantity    of 

(table),  and  function, 44 

Carbonate  of  potassa,  and  carbon- 
ate of  magnesia, 45 

Cartilagine, 91 

Cardiometer     of    Magendie    and 

Bernard, 263,  265 

of  Marey  (differential), 264 

Carbonaceous  matter  in  the  lungs,  364 

Carbonic  acid,  discovery  of, 410 

—  exhalation  of,  in  respiration,  424 

influence  of  arrest  of  respira- 
tory movements  on  exhalation 

of, 425 

quantity  of,  exhaled, 427 

influence  of  age  on  exhala- 
tion of, 431 

influence  of  sex, 432 

influence  of  digestion, 433 

influence  of  diet, 435 

influence  of  alcohol, 437 

influence  of  sleep, 439 

influence    of   moisture  and 

temperature, 441 

influence  of  seasons, 442 

'• sources  of,    in    the   expired 

air, 445 

proportion    in   arterial    and 

venous  blood, 464 

condition  of,  in  the  blood, . .  467 

effect  of  inhalation  of, 492 

production  of,  in  respiration,  478 

Carbonic  oxide,  exhalation  of,  by 
the  lungs  when  injected  into  the 

blood, 450 

Caseine,  extraction  of,  etc, 86 

Catalysis,  definition  of, 74 

Cephalo-rachidian  fluid,  uses  of, . .   334 

Chloride  of  sodium, 35 

quantity  of  (table), ....     35 

function  of, 36 


INDEX. 


499 


Chloride  of  sodium,  desire  of  all 

animals  for, 37 

effect  of  deprivation  of,  on 

nutrition, 37 

quantity  of  in  blood  almost 

constant, 38 

removal  of  excess  of  by  the 

kidneys, 38 

Chloride  of  potassium, 39 

Chloride  of  ammonium, 47 

Circulation  of  the  blood,  discovery 

of, 170 

general  course  of, 175 

action  of   the  heart  in  (see 

Heart), 177 

in    the     arteries     (see    Ar- 
teries),   240 

in  the  capillaries  (see  Capil- 
laries),    278 

in  the  veins  (see  Veins), . . .  301 

Circulation,  derivative, 339 

pulmonary, 340 

general  rapidity  of, 343 

rapidity  of,  in  different  ani- 
mals,   346 

relations  of  rapidity  of,  to  the 

frequency  of  the  heart's  action,  348 
Circulatory  system,  phenomena  in, 

after  death, 351 

Clot,  characters  of, 144 

Coloring  matters, 92 

Cornplemental  air, 401 

Convulsions  from  hemorrhage, ...  486 

Coughing, 395 

Coagulation    of    the    blood    (see 

Blood), 142 

Cranial  cavity,  circulation  in,. ...  332 
amorphous  sheath  of  blood- 
vessels of, 336 

Crystalline, 90 

Diabetic  sugar, 50 

Diaphragm,  action  of,  in  respira- 
tion,    369 

Diffusion  of  air  in  the  lungs, 406 

Elasticine, 91 

Emulsion, 63 

Emphysema,  changes  of  thorax  in,  385 

Epiglottis,  action  of,  in  deglutition,  359 

Erectile  tissues,  circulation  in,. . . .  336 

Erection,  mechanism  of, 338 

Expiration,  movements  of, 382 

influence  of  elasticity  of  the 

lungs  and  thoracic  walls  in, ....  383 
muscles  of  (table), 385 


Expiration,  action  of  internal  iuter- 

costals  in, 386 

action  of  infra-costales  and 

triangularis  sterni  in, 387 

action  of  obliquus  externus 

and  internus  in, 388 

action  of  transversalis  in, ...  388 

action  of  sacro-lumbalis  in, . .  389 

Fats,  varieties  of,  &c 60 

composition    and  properties 

of, ........  61 

condition  of,  in  nervous  tissue 

and  blood-corpuscles,.. 62 

saponification  of, 62 

emulsion  of, (53 

origin  and  functions  of,  ....  63 

formation  of,  in  the  organ- 
ism,    64 

average  quantity  of,  in  the 

body,     and    mechanical    func- 
tion of, 65 

changes  which  they  undergo 

in  the  organism, 66 

Fatty  acids, .. 62,  66 

Fermentation  of  sugar, 51 

Fermentation-test  for  sugar, 56 

Fibrin, 76 

mode  of  extraction  of,  and 

condition  in  the  organism, 77 

organization  of, 78 

distinctions      from      plastic 

lymph, 79 

origin  of, 80 

function  of,  and  destruction 

by  liver  and  kidneys, 81 

Gases,  as  proximate  principles,.. .  29 

in  the  alimentary  canal,. ...  29 

proportions  of,  in  venous  and 

arterial  blood, 456,  464-470 

of  the  blood,  table  of 

Magnus, 463 

Gases,  condition  of,  in  the  blood, .  466 

Globuline, 90 

Glucose, 50 

Glycerine, 62 

Hsematoidine, 117 

Heart,  anatomy  of, 176 

capacity  of  different  cavities 

of, 179 

valves  of, 181 

movements  of, 183 

action  of  the  auricles,... .,  184 

action  of  the  ventricles, ...  185 


500 


INDEX. 


Heart,  locomotion  of, 186 

twisting,  hardening,  short-  . 

ening,  and  elongation  of, 187 

-impulse  of, 191 

succession  of  movements  of,  192 

force  of, 197 

action  of  the  valves, 199 

sounds  of, 203 

cause  of  the  sounds  of, 207 

relations  of  the  sounds  to 

the  blood-currents, 210 

frequency  of  action  of, 211 

influence  of  age  and  sex  on 

frequency, 212 

influence  of  posture  and  mus- 
cular exertion, 213 

influence  of  exercise, 215 

influence  of  sleep, 216 

influence  of  temperature, ...  216 

influence  of  respiration  on 

action  of, 217 

cause  of  rhythmical  contrac- 
tions of, 220 

irritability  of, 222 

pulsations  of,  after  removal 

from  the  body, 223 

effect  of  ligature  of  coronary 

arteries  on  pulsations  of, 225 

effect  of  emptying  the  cavi- 
ties,    226 

influence  of  the  nervous  sys- 
tem on, 228 

influence  of  pneumogastrics 

on, 231 

effects  of  blows  on  epigastrium 

on, 238 

Hsematine, 92 

Hsematosis, 452 

Haemodynamometer    of     Poiseu- 

ille, 262,  265 

registering     instrument     of 

Ludwig  (note), 264 

differential  instrument  of  Ber- 
nard (note), 266 

Hydro-carbons,  general  considera- 
tions,   26,  48 

Hydro-chlorate  of  ammonia, 47 

Inorganic  principles,  general  con- 
siderations,      25 

table  of, 28 

division  into  essential  constit- 
uents of  the  tissues  and  those 

•which  influence  nutrition, 47 

Inspiration,  muscles  of  (table),.. . .  368 

action  of  diaphragm  in, 369 

— —  action  of  scaleni, 372 


Inspiration,  action  of  intercostals, .   373 

movements  of,  the  ribs  in, ...   374 

action  of  levatores  costarum,  378 

auxiliary  muscles  of, 378 

action  of  serratus  posticus 

superior, 378 

• action  of  sterno-mastoideus, 

levator  anguli  scapuloe,  and  su- 
perior portion  of  trapczius,. . . .   379 

action  of  pectoralis  minor, 

.inferior    portion    of   pectoralis 
major,  and  serratus  magnus,. ..  380 
Intercostals,  internal,  action  of,  in 

respiration, 386 

Infra-costales,  action  of,  in  respira- 
tion,    387 

Keratine, 91 

Lactic  acid, 67 

sources  and  function  of,. ...     68 

Larynx,  anatomy  and  respiratory 

movements  of, 358 

Laughing, 396 

Levatores  costarum,  action  of,  in 

respiration, 378 

Levator  anguli  scapulae,  action  of, 

in  respiration, 379 

Leucocytes, 121 

development  of, 124 

proportion  of,  to  red  corpus- 
cles,   125 

Liver,  influence  of  respiration  on 

circulation  in, 322 

Liver-sugar, 50 

Lungs,  anatomy  of  parenchyma  of,  361 

capacity  of, 397 

carbonaceous  matter  in, ....  364 

vital  capacity  of, 403 

Melanine, 93 

Milk-sugar, 50 

Mucosine, 89 

Musculine, 90 

Nitrogen,  exhalation  of,  in  respira- 
tion,  451 

of  the  blood, 465,  468 

Nitrogenized  principles,  general 
considerations, 27,  69 

Nitrous  oxide,  effects  of  respira- 
tion of, 415 

Non-nitrogenized  principles,. . .  25,  48 

Obliquus  externus  and  internus, 
action  of,  in  respiration, 388 


INDEX. 


501 


Odorous  principles, 66 

exhalation  of,  by  the  lungs, .  450 

Organic    non-nitrogenized    princi- 
ples, general  considerations,..  27,  69 
Organic    nitrogenized    principles,  . 
composition,    properties,     and 
condition  of,  in  the  organism, ..     71 

table  of, 75 

summary  of  properties  of, ...     93 

Organic  matter,  exhalation  of,  in 

respiration, 449 

Osteine, 91 

Otoconies,  or  otoliths, 18 

Oxygen,  discovery  of, 412 

minimum  proportion  in  the 

air  which  will  support  life, 414 

effects  of  confining  animals 

in  atmosphere  of, 415 

consumption  of,  in  respira- 
tion,   416,  476 

influence  of  age  on  consump- 
tion of, 421 

influence  of  temperature, ....  420 

consumption  of,  in  hiberna- 
tion,   422 

absorption  of,  by  blood-cor- 
puscles,  455 

proportion    in    arterial    and 

venous  blood, 464 

condition  of,  in  the  blood, . .  466 

Ozone, 414 

Pancreatine, 88 

Pepsin, 88 

Pectoral  muscles,  action  of,  in  res- 
piration,    380 

Phosphate  of  lime  (table  of  quan- 
tity of ), 40 

Phosphates  of  magnesia,  soda,  and 

potassa, 45 

Physiology,  definition  of, 14 

Piezometer  (note), 267 

Pneumic  acid, 68 

action  of,  on  the  bicarbonates 

in  the  blood, 446 

Pneumate  of  soda, 69 

Poisonous  gases,  exhalation  of,  by 

the  lungs, 450 

Proximate  principles,  general  con- 
siderations,    20-24 

inorganic, 25 

do.  (table), 28 

organic  non-nitrogenized, ...  25 

organic  nitrogenized, 27 

Proteine, 73 

Pulmonary    artery,    pressure    of 

blood  in, 341 


Pulse,  mechanism  of  production  of,  252 

.frequency  of, 212 

form  of, 254 

dicrotic, 257 

variations  in  character  of,. . .   260 

influence  of  temperature  on,  260 

Putrefaction, 73 

Rennet, 87 

Respiration,  influence  of,  on  the 

action  of  the  heart, 217 

general  considerations, '. . . . .  353 

movements  of, 366 

frequency  of  movements  of,.  391 

movements  of  ribs  in, 374 

types  of, 389 

relations  of  inspiration  and 

expiration, 392 

relations    in  volume   of   in- 
spired and  expired  air, 405 

changes  of  air  in  (historical 

considerations), 409 

consumption  of    oxygen    in 

(see  Oxygen), 416 

effect  of  confining  an  animal 

in  a  mixture  of  oxygen  and  hy- 
drogen,  422 

exhalation  of  carbonic   acid 

(see  Carbonic  Acid), 424 

relations  between  the  quan- 
tity of    oxygen  consumed   and 

carbonic  acid  exhaled, 443 

exhalation  of  watery  vapor, . .  446 

exhalation  of  ammonia,. . . .  448 

exhalation  of  organic  matter,  449 

exhalation  of  alcohol, 450 

exhalation  of  odorous  princi- 
ples,   450 

exhalation  of  certain  poison- 
ous gases, 450 

exhalation  of  nitrogen, 451 

changes  of  the  blood  in, ....  452 

absorption  of  oxygen  by  the 

blood-corpuscles, 455 

proportions  of  gases  in  venous 

and  arterial  blood, . . .  456,  464-470 

relations  of,  to  nutrition, ....  472 

combustion-theory  of,. .  473-476 

consumption  of  oxygen, 476 

production  of  carbonic  acid,  478- 

cutaneous, 489 

Respiratory  organs,  anatomy  of,..  357 
Respiratory  sounds  (murmurs),. . .   393 
Respiratory  sense,  the  sensation 
inducing      respiratory      move- 
ments,  479-484 

Respiratory  efforts  before  birth,. . .  487 


502 


INDEX. 


Kesidual  air, 399 

Reserve  air, 400 

Saponification, 62 

Sacro-lumbalis,  action  of,  in  res- 
piration,   389 

Scalene  muscles,  action  of,  in  res- 
piration,    372 ' 

Serratus  posticus  superior,  action 

of,  in  respiration, 378 

Serratus  magnus,  action  of,  in  res- 
piration,   380 

Serum,  characters  of, 146 

Sighing, 396 

Sleep,  cerebral  circulation  in, 334 

Snoring, 393 

Sneezing, 395 

Sobbing, 396 

Soaps, 62-66 

Sphygmograph  of  Marey, 255 

ofVierordt, 256 

Sterno-mastoideus,  action  of,  in  res- 
piration,   379 

Sulphates  of  soda,   potassa,  and 

lime,. 46 

Sulphuretted  hydrogen,  exhalation 

of,  by  the  lungs, 450 

Sugar, 49 

varieties  of, 50 

union  of,  with  chloride  of 

sodium, 50 

composition  and  properties 

of, 50 

fermentation  of, 51 

lactic-acid  fermentation  of, ..  51 

influence  of   solution  of  on 

polarized  light, 52 

tests    for,    Moore's    or  the 

potash  test,  Trommer's  test,. ...  52 

BarreswilFs  test, 55 

Maumene's   test,    fermenta- 
tion test,  Bottger's  test, 56 

formation  of  torula?, 58 

origin  and  functions  of, ....  58 

formation  of,  hi  the  foetus, 

and  influence  on  cell-develop- 
ment,    59 

destruction  of,  in  the  lungs, .  59 

Suffocation,  sense  of, 484 

Tidal  air, 401 


Torulae  cerevisia?, 58 

Transfusion  of  blood,. 97-99 

Transversalis,  action  of,   in    res- 
piration,    388 

Trapezius,  action  of,  in  respiration,  379 

Trachea,  anatomy  of, 360 

Triangularis  sterni,  action  of,  in  res- 
piration,    387 


Urrosaoine,. 


Valves  of  the  veins,  discovery  of, .   172 
Valves  of  the  heart  (see  Heart),. . .    181 

Vasa  vasorum, 245 

Veins,  anatomy  of, 301 

capacity  of, 302 

strength  of, 306 

valves  of, 308 

function  of  valves  of, 325 

course  of  blood  in, 311 

pressure  of  blood  in, 314 

rapidity  and  causes  of  circu- 
lation in, 315 

influence  of   muscular  con- 
traction on  current  of  blood  in,  817 

influence  of  aspiration  from 

the  thorax, 319 

influence  of  gravitation,  324-330 

entrance  of  air  into, 323 

conditions  which  impede  cir- 
culation in, 328 

influence    of    expiration  on 

current  of  blood  in, 328 

Venous  pulse, 313 

Venous  pulse,  regurgitant, 329 

Vital  properties  of  organized  struc- 
tures,      18 

Vital  capacity  of  the  lungs, 403 

Water,  as  a  proximate  principle, .      30 
condition  of,  in  the  organ- 
ism,    30 

quantity  of,  in  different  parts, 

(table), 33 

entire  quantity  in  the  body, .     48 

origin,  discharge,  and  func- 
tion of, 34 

Watery  vapor,  exhalation  of,   in 
respiration, 446 

Yawning, 396 


"A  BOOK  WHICH  13  A3  READABLE  AS  A  NOVEL: 


HISTORY  OF  EUROPEAN  MORALS, 

From  Augustus  to    Charlemagne. 

By  W.  E.  H.  LECKY,  M.  A. 

2  vols.,  8vo.     500  pages  each.    Price,  $6.00. 


CONTENTS  : 

The  Utilitarian  School— Objections  to  the  School— Consequence  of  acting 
on  Utilitarian  Principles— Utilitarian  Sanctions— Intuitive  School— Alleged 
Diversities  of  Moral  Judgment— Each  of  the  Two  Schools  of  Morals  related 
to  the  General  Condition  of  Society— The  Order  in  which  Moral  Feelings 
are  developed. 

THE  PAGAN  EMPIRE. 

Stoicism— Growth  of  a  Gentler  and  more  Cosmopolitan  Spirit  in  Rome— 
Rise  of  Eclectic  Moralists— The  People  still  very  corrupt— Causes  of  the 
Corruption — Effects  of  Stoicism  en  the  Corruption  of  Society — Passion  for 
Oriental  Religions— Neoplatonism. 

THE  CONVERSION  OF  ROME. 

Examination  of  the  Theory  which  ascribes  part  of  the  Teaching  of  the 
Hated  Pagan  Moralists  to  Christian  Influence— Theory  which  attributes  the 
Conversion  of  the  Empire  to  the  Evidence  of  Miracles — The  Persecution  the 
Church  underwent  not  of  a  Nature  to  crush  it— History  of  the  Persecutions. 

FROM  CONSTANTINE  TO  CHARLEMAGNE. 

First  Consequence  of  Christianity,  a  New  Sense  of  the  Sanctity  of  Hu- 
man Life— The  Second  Consequence  of  Christianity,  to  teach  Universal 
Brotherhood — Two  Qualifications  of  our  Admiration  of  the  Charity  of  the 
Church— The  Growth  of  Asceticism— The  Saints  of  the  Desert— Decline  of 
the  Civic  Virtues— General  Moral  Condition  of  the  Byzantine  Empire— Dis- 
tinctive Excellences  of  the  Ascetic  Period — Monach4sm — Relation  of  Mona- 
chism  to  the  Intellectual  Virtues— The  Monasteries  the  Receptacles  of 
Learning— Moral  Condition  of  Western  Europe— Growth  of  a  Military  and 
Aristocratic  Spirit— Consecration  of  Secular  Rank. 

THE  POSITION  OF  WOMEN. 

The  Courtesans— Roman  Public  Opinion  much  purer— Christian  Influ- 
ence—Relation of  Christianity  to  the  Female  Virtues. 

D.  APPLETON  &  CO.,  Publishers, 

90,  92  &  94  GRAND  ST.,  NEW  YORK. 
Sent  free  by  mall  to  any  address  in  the  United"  States  on  receipt  of  the  price. 


D.  APPLETOX  &  CO.'S  PUBLICATIONS. 


THE  ONLY  COMPLETE  AND  TOITOEM  EDITION, 


LORD  MACAULAY'S  WORKS, 

EDITED  BY  HIS   8I8TEE, 

JL,^LDY     T  REV  ELY  .A.  IN". 

8  Vols.,  large  8vo.     Price,  cloth,  $40.00  ;   half  calf  extra, 

$56.00  ;  full  calf  extra,   $64.00.    Beautifully  printed  in 

large  clear  type,  on  thick  toned  paper,  with  a  fine 

portrait  engraved  on  steel  by  W.  Holl. 


In  preparing  for  publication  a  complete  and  uniform  edition  of  Lord 
Macaulay's  Works,  it  has  been  thought  right  to  include  some  portion  of  what 
he  placed  on  record  as  a  jurist  in  the  East.  The  papers  selected  are  the  Intro- 
ductory Eeport  on  the  Indian  Penal  Code,  and  the  Notes  appended  to  that  code, 
in  which  most  of  its  leading  provisions  were  explained  and  defended.  These 
papers  were  entirely  written  by  Lord  Macaulay,  but  the  substance  ol  them  was 
the  result  of  the  joint  deliberations  of  the  Indian  Law  Commission,  of  which 
he  was  President.  They  are  by  no  means  merely  of  Indian  interest,  for  while 
they  were  the  commencement  of  a  new  system  of  law  for  India,  they  relate 
chiefly  to  general  principles  of  jurisprudence,  which  are  of  universal  applica- 
tion. 

The  contents  are  arranged  in  this  edition  as  follows :  Yols.  I.  to  IV.,  History 
of  England  since  the  Accession  of  James  the  Second ;  Vols.  V,,  VI.,  and  VII., 
Critical  and  Historical  Essays,  Biographies,  Eeport  and  Notes  on  the  Indian 
Penal  Code,  and  contributions  to  Knight's  Quarterly  Magazine;  Vol.  VIII., 
Speeches,  Lays  of  Ancient  Rome,  and  Miscellaneous  Poems. 

This  last  division  of  the  work  is  completed  by  the  insertion  of  the  Cavalier's 
Song  and  the  Poetical  Valentine  to  the  Hon.  Mary  C.  Stanhope,  two  pieces 
which  were  not  included  in  previous  editions  of  Lord  Macaulay1s  miscellaneous 
writings. 

"  Every  admirer  of  Lord  Macaulay's  writings  (and  their  name  is  legion) 
will  heartily  thank  Appleton  &  Co.  for  having  produced  this  elegant  edition  of 
his  works.  It  seems  almost  idle  to  say  any  thing  in  praise  of  the  great  his- 
torian to  the  American  reader,  but  wo  cannot  forbear  expressing  our  admiration 
of  the  physical  as  well  as  mental  strength  so  manifest  in  his  diction  and  style. 
....  But  it  is  not  our  intention  to  write  a  critique  on  the  man  whose 
memory  holds  so  prominent  a  placa  in  the  heart  of  the  reading  world.  The 
volumes  before  us  should  fill  a  niche  in  every  public  and  private  library  in  our 
land." — Glen  falls  Journal. 

"  His  writings  and  his  speeches,  arranged  in  chronological  order,  exhibit  the 
developments  of  a  mind  always  more  or  less  powerful,  and  announce  the  ex- 
tent of  his  reading  and  the  tenacity  of  his  memory.  His  contributions  to  the 
History  of  British  India  show  how  usefully  his  time  was  spent  during  his  so- 
journ at  Calcutta." 


D.  Appleton  &  Co. '3  Descriptive  Catalogue  may  be  had  gratuitously 
om  application. 

D.  APPLETON  &  CO., 

Publishers,  Booksellers,  &  Stationers, 

90,  92  &  94  GRAND  STREET,  NEW  YORK. 


RETURN      BIOLOGY  LIBRARY 

TO— ^      3503  Life  Sciences  Bldg.     642-2531 


LOAN  PERIOD  1      2 


ALL  BOOKS  MAY  BE  RECALLED  AFTER  7  DAYS 
Renewed  books  are  subject  to  immediate  recall 


DUE  AS  STAMPED  BELOW 

WW  2  8  1990 

•**WV 

v 

MAY  2  R  1991 

r- 

TH  \  6  w^ 

,  ,v 

i 

UNIVERSITY  OF  CALIFORNIA,  BERKELEY 
FORM  NO.  DD4,  12m,  12/80        BERKELEY,  CA  94720 


RETURN     BIOLOGY  LIBRARY 


